Periodic Table of Elements

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1

H

Hydrogen

1.007

Hydrogen is an odorless, inflammable gas, which only occurs naturally on Earth in compounds.

State: diatomic gas, H2 at standard conditions

Type: non-metal, Group: 1, Period: 1

Electron configuration: 1s1

Discovered By: Henry Cavendish in 1766 (Unit 2, Section 5).

Common Use: Hydrogen is made by the reaction of water, gas, and steam over a catalyst. It is a reducing agent, burns in air with a light blue flame, and when heated, reacts with many substances. Hydrogen is used to make ammonia for plant fertilizer (see Unit 7, Section 9 and Unit 9, Section 9).

1 H 1.007

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2

He

Helium

4.003

Helium is a light, colorless inert gas under standard conditions.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 1

Electron configuration: 1s2

Discovered By: In 1868, astronomers Jules Janssen and Norman Lockyer are jointly credited with discovering the element. Janssen, though a French astronomer, observed it during the solar eclipse from India while Lockyer observed it from his native Britain. Lockyer was the first to propose that the line was due to a new element, which he named 'Helium.' The formal discovery of the element was made in 1895 by two Swedish chemists, Per Teodor Cleve and Nils Abraham Langlet, and a Scottish chemist, Sir William Ramsay, who found helium emanating from the uranium ore cleveite.

Common Use: Helium is mainly used to cool MRI scanners' superconducting magnets. It is also used to fill ballons and pressurize liquid fuel rockets (see Unit 3, Section 6).

2 He 4.003

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3

Li

Lithium

6.938

Lithium is a silvery, soft, light metal that is solid at room temperature.

State: solid at standard conditions

Type: alkali metal, Group: 1, Period: 2

Electron configuration: 1s2 2s1

Discovered By: Johan August Arfwedson in 1817.

Common Use: Lithium has several industrial applications, including heat-resistant glass and ceramics, high strength-to-weight alloys used in aircraft, and lithium batteries. These uses consume more than half of lithium production. Trace amounts of lithium are present in all organisms; however, its purpose is not known. The lithium ion Li+ has proved to be useful as a mood-stabilizing drug in the treatment of bipolar disorder. It has important links to nuclear physics. Lithium deuteride serves as a fusion fuel in staged thermonuclear weapons.

3 Li 6.938

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4

Be

Beryllium

9.01

Beryllium is a light, silver-gray, soft metal that is solid at room temperature.

State: solid at standard conditions

Type: alkaline earth metal, Group: 2, Period: 2

Electron configuration: 1s2 2s2

Discovered By: Louis Nicolas Vauquelin in 1797.

Common Use: Beryllium is used as a lightweight structural material for high-speed aircraft, communication satellites, and other spacecraft. Unlike other metals, x-rays can pass through beryllium, making it an important component of radiation windows for x-ray tubes.

4 Be 9.01

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5

B

Boron

10.81

Boron is a black or brown powder at room temperature.

State: solid at standard conditions

Type: metalloid, Group: 13, Period: 2

Electron configuration: 1s2 2s2 2p1

Discovered By: Joseph Louis Gay-Lussac and Louis Jacques Thénard, and independently by Humphry Davy in 1808.

Common Use: Boron is used in fireworks to provide a distinctive green color. Boron's most important compounds include boric acid and borax, which are used in many different cleaning products. Boron is also used to make different types of glass; the boric acid used in making Pyrex glass makes it tough and heat resistant.

5 B 10.81

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6

C

Carbon

12.01

Carbon can appear black as in graphite, or transparent as in diamond, and is solid at room temperature.

State: solid at standard conditions

Type: non-metal, Group: 14, Period: 2

Electron configuration: 1s2 2s2 2p2

Discovered By: Egyptians and Sumerians in ancient times.

Common Use: Carbon (from latin "carbo": meaning coal) is unique among the elements in the large variety of compounds it can form. Carbon is one of the few elements known since antiquity as it was used in the form of charcoal by the Egyptians and Sumerians. It is very widely distributed in nature, and used in many forms of industry. Carbon is very different depending on the way the carbon atoms are structured, forming both diamond and graphite, along with many other formations. It is an important part of DNA and proteins, and it is found in abundance in the sun, stars, and atmospheres of most planets. It is also an indispensable source of such varied everyday products as Nylon, perfume, plastics, shoe polish, and TNT.

6 C 12.01

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7

N

Nitrogen

14.01

Nitrogen is a colorless, odorless, tasteless gas under standard conditions.

State: gas at standard conditions

Type: non-metal, Group: 15, Period: 2

Electron configuration: 1s2 2s2 2p3

Discovered By: Daniel Rutherford in 1772.

Common Use: Like hydrogen, nitrogen is mostly used to make ammonia for plant fertilizer (see interactive).

7 N 14.01

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8

O

Oxygen

16

Oxygen is a colorless, odorless gas under standard conditions.

State: gas at standard conditions

Type: non-metal, Group: 16, Period: 2

Electron configuration: 1s2 2s2 2p4

Discovered By: Joseph Priestley and independently by Carl Wilhelm Scheele in 1774.

Common Use: Oxygen makes up approximately 21% of the Earth's atmosphere, and is essential to life. Most commercially produced oxygen gas (O2) is used to make steel (see Unit 13, Section 6 sidebar).

8 O 16

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9

F

Fluorine

19

Fluorine is a pale yellow gas under standard conditions.

State: gas at standard conditions

Type: halogen, Group: 17, Period: 2

Electron configuration: 1s2 2s2 2p5

Discovered By: Humphrey Davy in 1813, and first isolated by Henri Moissan in 1886.

Common Use: Fluorine and its compounds (mostly uranium hexafluoride) are used to process nuclear fuel.

9 F 19

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10

Ne

Neon

20.18

Neon is a colorless, odorless gas under standard conditions.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 2

Electron configuration: 1s2 2s2 2p6

Discovered By: William Ramsay & Morris Travers in 1898.

Common Use: Neon is often used in brightly lit advertising signs, since it glows orange-red when a current is applied to it (see Unit 3 video).

10 Ne 20.18

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11

Na

Sodium

22.99

Sodium is a soft, silvery white metal. It burns in air with an orange-yellow flame and reacts violently with non-metals and water.

State: solid at standard conditions

Type: alkali metal, Group: 1, Period: 3

Electron configuration: 1s2 2s2 2p6 3s1

Discovered By: Sir Humphry Davy in 1807.

Common Use: Sodium can be found in many compounds. It is extracted from molten sodium chloride by electrolysis of molten sodium chloride, using a Downs' cell. It is used in sodium vapor lamps and as a coolant in nuclear power stations. (See Unit 3, Section 6.)

11 Na 22.99

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12

Mg

Magnesium

24.31

Magnesium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: alkaline earth metal, Group: 2, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2

Discovered By: Joseph Black in 1755.

Common Use: Magnesium is widely used in the production of cell phones, cameras, laptops, and other electronic components. It is also used to remove sulfur in the production of iron and steel. (See Unit 7, Section 8.)

12 Mg 24.31

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13

Al

Aluminum

26.98

Aluminum is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 13, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2 3p1

Discovered By: Hans Christian Ørsted in 1825.

Common Use: Because of its low density, low cost, and resistance to corrosion, aluminum is widely used around the world everywhere from soda cans to aircraft (see Unit 11, Section 7).

13 Al 26.98

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14

Si

Silicon

28.09

Silicon is a silvery, reflective solid at room temperature.

State: solid at standard conditions

Type: metalloid, Group: 14, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2 3p2

Discovered By: Jöns Jacob Berzelius in 1823.

Common Use: Silicon is one of the most useful of all the elements. Silicon chips are the basis of modern electronics. Sand, clay, and steel all contain silicon. (See Unit 1 video.)

14 Si 28.09

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15

P

Phosphorus

30.97

Phosphorous is a mineral that has many different varieties, that appear colorless, white, yellow, scarlet, red, and violet, and is solid at room temperature.

State: solid at standard conditions

Type: non-metal, Group: 15, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2 3p3

Discovered By: Hennig Brand in 1669.

Common Use: Phosphorus is important in the production of fertilizer and steel (see Unit 13, Section 6 sidebar).

15 P 30.97

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16

S

Sulfur

32.07

Sulfur is a bright yellow crystalline solid at room temperature.

State: solid at standard conditions

Type: non-metal, Group: 13, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2 3p4

Discovered By: People before 2000 BCE.

Common Use: Sulfur is used in black gunpowder, to vulcanize black rubber, and as a fungicide. It is also used to produce sulfuric acid (H2SO4), which is an important manufactured chemical used in car batteries and drain cleaners. (See also Unit 10, Section 5 sidebar.)

16 S 32.07

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17

Cl

Chlorine

35.45

Chlorine is a greenish-yellow gas under standard conditions.

State: gas at standard conditions

Type: halogen, Group: 17, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2 3p5

Discovered By: Carl Wilhelm Scheele in 1774.

Common Use: Chlorine is used to produce safe drinking water, and to disinfect swimming pools and many consumer products such as paper, textiles, medicines, insecticides, foodstuffs, and plastics.

17 Cl 35.45

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18

Ar

Argon

39.95

Argon is a colorless gas at under standard conditions.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 3

Electron configuration: 1s2 2s2 2p6 3s2 3p6

Discovered By: Lord Rayleigh and William Ramsay in 1894.

Common Use: Because of how unreactive it is, argon is used in light bulbs to protect the filament and to provide a safe atmosphere for welding.

18 Ar 39.95

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19

K

Potassium

39.10

Potassium is a soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: alkali metal, Group: 1, Period: 4

Electron configuration: [Ar] 4s1

Discovered By: Sir Humphry Davy in 1807.

Common Use: Potassium is often used in fertilizers, because is essential for plant growth. (See Unit 4 video.)

19 K 39.10

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20

Ca

Calcium

40.08

Calcium is a soft, silver-gray metal that is solid at room temperature.

State: solid at standard conditions

Type: alkaline earth metal, Group: 2, Period: 4

Electron configuration: [Ar] 4s2

Discovered By: Humphry Davy in 1808.

Common Use: Calcium is used in alloys and in the extraction of other metals. (See Unit 6, Section 7).

20 Ca 40.08

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21

Sc

Scandium

44.96

Scandium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 3, Period: 4

Electron configuration: [Ar] 3d1 4s2

Discovered By: Lars Fredrik Nilson in 1879.

Common Use: Scandium is used in aluminum-scandium alloys for sports equipment such as fishing rods, bicycle frames, and baseball bats, as well as aerospace industry components. (See Unit 12, Section 8.)

21 Sc 44.96

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22

Ti

Titanium

47.87

Titanium is a silvery-white, low density, strong metal that is solid at room temperature.

State: solid at standard conditions

Type: transiiton metal, Group: 4, Period: 4

Electron configuration: [Ar] 3d2 4s2

Discovered By: William Gregor in 1791.

Common Use: Titanium is as strong as steel but much less dense, and can withstand extremes of temperature, and is resistant to sea eater. Titanium alloys are used in aircraft, missiles, and in the hulls of ships (see Unit 13, Section 9).

22 Ti 47.87

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23

V

Vanadium

50.94

Vanadium is a silvery-gray, malleable metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 5, Period: 4

Electron configuration: [Ar] 3d3 4s2

Discovered By: Andrés Manuel del Río in 1801.

Common Use: Most of the vanadium produced is used as a steel additive, which greatly increases its strength, toughness, and heat resistance (see Unit 13, Section 9).

23 V 50.94

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24

Cr

Chromium

52.00

Chromium is a is a steely-gray, lustrous, hard metal.

State: solid at standard conditions

Type: transition metal, Group: 5, Period: 4

Electron configuration: [Ar] 3d5 4s1

Discovered By: Louis Nicolas Vauquelin in 1797.

Common Use: Chromium plating on cars and bicycles produces a smooth, shiny finish that is corrosion resistant (see Unit 13, Section 9).

24 Cr 52.00

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25

Mn

Manganese

54.94

Manganese is a gray-white, hard, brittle metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 7, Period: 4

Electron configuration: [Ar] 3d5 4s2

Discovered By: Johann Gottlieb Gahn in 1774.

Common Use: Manganese to produce a variety of important alloys, including the aluminum alloy that allows soda cans to be so thin. It's also used to neutralize green in glass caused by iron impurities. (See Unit 13, Section 10.)

25 Mn 54.94

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26

Fe

Iron

55.85

Iron is a silvery-gray metal.

State: solid at standard conditions

Type: transition metal, Group: 8, Period: 4

Electron configuration: [Ar] 3d6 4s2

Discovered By: People in ancient times.

Common Use: Iron is the cheapest and most commonly used metal. Iron is used to produce steel and other alloys important in construction and manufacturing. (See Unit 13, Section 6, sidebar.)

26 Fe 55.85

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27

Co

Cobalt

58.99

Cobalt is a hard, bluish-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 9, Period: 4

Electron configuration: [Ar] 3d7 4s2

Discovered By: Georg Brandt in 1732.

Common Use: Cobalt salts are used to produce brilliant blue and green colors in glass, porcelain, and ceramics. Cobalt alloys are used for aircraft engine parts. (See Unit 11, Section 10.)

27 Co 58.99

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28

Ni

Nickel

58.69

Nickel is a silvery-white lustrous metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 10, Period: 4

Electron configuration: [Ar] 3d8 4s2

Discovered By: Axel Fredrik Cronstedt in 1751.

Common Use: Nickel is used in many common items including stainless steel, magnets, coins, rechargeable batteries, and electric guitar strings. It's also used in gas turbines and rocket engines because of its resistance to corrosion at high temperatures. (See Unit 11, Section 7.)

28 Ni 58.69

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29

Cu

Copper

63.55

Copper is a orange-red, soft metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 11, Period: 4

Electron configuration: [Ar] 3d10 4s1

Discovered By: Ancients before 4300 BCE.

Common Use: Because of its high conductivity, it is most commonly used in electrical wiring and motors. All American coins contain copper. (See Unit 13, Section 5.)

29 Cu 63.55

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30

Zn

Zinc

65.38

Zinc is a bluish-silver metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 12, Period: 4

Electron configuration: [Ar] 3d10 4s2

Discovered By: Andreas Sigismund Marggraf in 1746.

Common Use: Zinc is used in alloys such as brass, nickel silver and aluminum solder. Zinc alloys are used in die-castings for the automobile and hardware industries. (See Unit 11, Section 7 sidebar and Unit 11, Section 9 sidebar.)

30 Zn 65.38

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31

Ga

Gallium

69.72

Gallium is a soft, silvery-blue metal, which melts close to room temperature.

State: Gallium is a solid at room conditions, but its melting point is just under 30°C

Type: post-transition metal, Group: 13, Period: 4

Electron configuration: [Ar] 3d10 4s2 4p1

Discovered By: Paul-Émile Lecoq de Boisbaudran in 1875.

Common Use: Gallium alloys are used in some thermometers as a non-toxic substitute for mercury. Gallium can also be painted on glass to make a brilliant mirror.

31 Ga 69.72

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32

Ge

Germanium

72.63

Germanium is a gray-white metalloid which is solid at room temperature.

State: solid at standard conditions

Type: metalloid, Group: 14, Period: 4

Electron configuration: [Ar] 3d10 4s2 4p2

Discovered By: Clemens A. Winkler in 1886.

Common Use: Because of its high index of refraction, geranium is used for for wide-angle camera lenses, in microscopes, and for the core part of optical fibers. Germanium is also used as a semiconductor. (See Unit 4, Section 2.)

32 Ge 72.63

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33

As

Arsenic

74.92

Arsenic is a gray metalloid that is solid at room temperature.

State: solid at standard conditions

Type: metalloid, Group: 15, Period: 4

Electron configuration: [Ar] 3d10 4s2 4p3

Discovered By: Albertus Magnus in 1250.

Common Use: Arsenic compounds are used in insecticides and wood preservation because of its toxicity. (See Unit 8, Section 4 sidebar.)

33 As 74.92

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34

Se

Selenium

78.96

Selenium is gray or red in its crystalline form, and black or red in its amorphous form.

State: solid at standard conditions

Type: non-metal, Group: 16, Period: 4

Electron configuration: [Ar] 3d10 4s2 4p4

Discovered By: Jöns Jacob Berzelius in 1817.

Common Use: Because of its reaction with sunlight, some selenium is used to produce efficient solar cells. Most selenium is used to decolorize glass or to tint glass red.

34 Se 78.96

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35

Br

Bromine

79.90

Bromine is a red-brown liquid at room temperature.

State: liquid at standard conditions

Type: halogen, Group: 17, Period: 4

Electron configuration: [Ar] 3d10 4s2 4p5

Discovered By: Antoine-Jérôme Balard and Leopold Gmelin in 1825.

Common Use: Bromine can be added to different materials to make them flame-retardant. It's also used to make photographic film. Bromine, like chlorine, can be used to maintain swimming pools and hot tubs. (See Unit 4, Section 3.)

35 Br 79.90

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36

Kr

Krypton

83.80

Krypton is a colorless, odorless, tasteless noble gas under standard conditions.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 4

Electron configuration: [Ar] 3d10 4s2 4p6

Discovered By: William Ramsay and Morris Travers in 1898.

Common Use: Krypton is used in many different types of lighting, such as high-powered airport runway lights, fluorescent tubes, bright lights for high speed photography, and greenish-yellow glowing signs. (See Unit 12, Section 9.)

36 Kr 83.80

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37

Rb

Rubidium

85.47

Rubidium is a soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: alkali metal, Group: 1, Period: 5

Electron configuration: [Kr] 5s1

Discovered By: Robert Bunsen and Gustav Kirchhoff in 1861.

Common Use: Rubidium is used to produce a purple color in fireworks. It can also be used in photocells and to make specialty glass. (See Unit 3, Section 6.)

37 Rb 85.47

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38

Sr

Strontium

87.62

Strontium is a soft, silvery-white or yellow metal that is solid at room temperature.

State: solid at standard conditions

Type: alkaline earth metal, Group: 2, Period: 5

Electron configuration: [Kr] 5s2

Discovered By: Adair Crawford in 1790.

Common Use: Strontium is mostly used to produce glass for cathode ray tubes used in early color TVs. Strontium can also be used to add the color red to glass and ceramics, and can provide the brilliant red color in certain kinds of fireworks. (See Unit 4, Section 8 sidebar.)

38 Sr 87.62

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39

Y

Yttrium

88.91

Yttrium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 3, Period: 5

Electron configuration: [Kr] 4d1 5s2

Discovered By: Johan Gadolin in 1794.

Common Use: Yttrium is often used to increase the strength of aluminum and magnesium alloys. Yttrium is also used to produce the red color in early color television tubes.

39 Y 88.91

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40

Zr

Zirconium

91.22

Zirconium is a grayish-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 4, Period: 5

Electron configuration: [Kr] 4d2 5s2

Discovered By: Martin Heinrich Klaproth in 1789.

Common Use: Zirconium is used to make superconductive magnets. Since Zirconium does not absorb many neutrons, it is often used in construction for nuclear reactors, and its resistance to corrosion makes it useful in the chemical industry.

40 Zr 91.22

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41

Nb

Niobium

92.91

Niobium is a soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 5, Period: 5

Electron configuration: [Kr] 4d4 5s1

Discovered By: Charles Hatchett in 1801.

Common Use: Niobium is used to increase the strength of steel. It is also used in jet engines and rockets. Niobium is also used in superconductive magnets which are used in MRI machines.

41 Nb 92.91

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42

Mo

Molybdenum

95.96

Molybdenum is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 6, Period: 5

Electron configuration: [Kr] 4d5 5s1

Discovered By: Carl Wilhelm Scheele in 1778.

Common Use: Molybdenum is mostly used to strengthen steel. It is also used in certain nickel-based alloys to make them heat and corrosion resistant. Molybdenum can withstand extreme temperatures, which makes it useful in manufacturing aircraft parts, electrical contacts, and motors. (See Unit 13 video.)

42 Mo 95.96

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43

Tc

Technetium

(98)

Technetium is a silver-gray metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 7, Period: 5

Electron configuration: [Kr] 4d5 5s2

Discovered By: Carlo Perrier and Emilio Segrè in 1937.

Common Use: Technetium is widely used for medical diagnostic studies, as several chemical forms can be used to image different parts of the body. (See Unit 12, Section 7.)

43 Tc (98)

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44

Ru

Ruthenium

101.07

Ruthenium is a hard, brittle silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 8, Period: 5

Electron configuration: [Kr] 4d7 5s1

Discovered By: Jędrzej Śniadecki in 1807.

Common Use: Ruthenium effectively strengthens platinum and palladium, and is alloyed with these metals to make wear-resistant electrical contacts.

44 Ru 101.07

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45

Rh

Rhodium

102.91

Rhodium is a hard silvery-white metal which is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 9, Period: 5

Electron configuration: [Kr] 4d8 5s1

Discovered By: William Hyde Wollaston in 1804.

Common Use: Rhodium is mainly used in automobiles as a catalytic converter, which changes harmful emissions from the engine into less harmful gases. Rhodium is also used in jewelry and decorations.

45 Rh 102.91

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46

Pd

Palladium

106.42

Palladium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 10, Period: 5

Electron configuration: [Kr] 4d10

Discovered By: William Hyde Wollaston in 1803.

Common Use: Palladium is mostly used in catalytic converters, which changes harmful emissions from the engine into less harmful gases. Palladium is also used to make jewelry, blood sugar test strips, and aircraft spark plugs.

46 Pd 106.42

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47

Ag

Silver

107.87

Silver is a soft, ductile metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 11, Period: 5

Electron configuration: [Kr] 4d10 5s1

Discovered By: People around 3000 BCE.

Common Use: Silver is used to make jewelry, silverware, and mirrors. Silver has the highest electrical and thermal conductivity of all metals, and is used to make electrical components. (See Unit 8, Section 10.)

47 Ag 107.87

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48

Cd

Cadmium

112.41

Cadmium is a soft bluish-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 12, Period: 5

Electron configuration: [Kr] 4d10 5s2

Discovered By: Karl Samuel Leberecht Hermann and independently by Friedrich Stromeyer in 1817.

Common Use: Cadmium is mostly used to produce rechargeable nickel-cadmium batteries.

48 Cd 112.41

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49

In

Indium

114.82

Indium is a soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 13, Period: 5

Electron configuration: [Kr] 4d7 5s2 5p1

Discovered By: Ferdinand Reich and Hieronymous Theodor Richter in 1863.

Common Use: Indium can be alloyed with gallium to make a metal that is liquid at room temperature, which can sometimes be used as a non-toxic alternative to mercury. Indium can also be used to make a mirror with better corrosion resistance than silver.

49 In 114.82

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50

Sn

Tin

118.71

Tin is a silvery-white, soft, malleable metal that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 14, Period: 5

Electron configuration: [Kr] 4d7 5s2 5p2

Discovered By: People in approximately 3000 BCE.

Common Use: Tin is used to treat other metals to prevent corrosion, such as in tin cans which are tin-coated steel. (See Unit 1, Section 3.)

50 Sn 118.71

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51

Sb

Antimony

121.76

Antimony is a silvery-white brittle crystalline solid at room temperature.

State: solid at standard conditions

Type: metalloid, Group: 15, Period: 5

Electron configuration: [Kr] 4d10 5s2 5p3

Discovered By: People in ancient times.

Common Use: Antimony is often alloyed with lead alloys for use in batteries. Antimony compounds are used to manufacture flame-proof compounds, enamels, paints, and glass. (See Unit 4, Section 3.)

51 Sb 121.76

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52

Te

Tellurium

127.60

Tellurium is a silvery-white, brittle metalloid that is solid at room temperature.

State: solid at standard conditions

Type: metalloid, Group: 16, Period: 5

Electron configuration: [Kr] 4d10 5s2 5p4

Discovered By: Franz-Joseph Müller von Reichenstein in 1782.

Common Use: Tellurium is alloyed with copper and stainless steel to make them more workable. It is also used to color ceramics.

52 Te 127.60

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53

I

Iodine

126.90

Iodine is a bluish-black, lustrous solid under standard conditions, and is purple as a gas.

State: solid at standard conditions

Type: halogen, Group: 17, Period: 5

Electron configuration: [Kr] 4d10 5s2 5p5

Discovered By: Bernard Courtois in 1811.

Common Use: Iodine is sometimes is added to table salt to prevent thyroid disease. It is also used as in medicine both as a disinfectant for external wounds and for internal medicine. (See Unit 13, Section 4.)

53 I 126.90

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54

Xe

Xenon

131.29

Xenon is a colorless, odorless, heavy gas under standard conditions.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 5

Electron configuration: [Kr] 4d10 5s2 5p6

Discovered By: William Ramsay and Morris Travers in 1898.

Common Use: Xenon is used in high-speed electronic flash bulbs used by photographers, and produces a blue glow inside a glass tube when excited by electricity. Modern space craft use inert gasses such as xenon for propellant. (See Unit 3 video.)

54 Xe 131.29

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55

Cs

Cesium

132.91

Cesium is silvery-gold soft metal that melts very close to room temperature.

State: solid at standard conditions

Type: alkali metal, Group: 1, Period: 6

Electron configuration: [Xe] 6s1

Discovered By: Robert Bunsen and Gustav Kirchhoff in 1860.

Common Use: Cesium is used in precise atomic clocks, which are used as the standard measure of time. (See Unit 3, Section 8.)

55 Cs 132.91

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56

Ba

Barium

137.33

Barium is a soft, silvery-white alkaline earth metal that is solid at room temperature.

State: solid at standard conditions

Type: alkaline earth metal, Group: 2, Period: 6

Electron configuration: [Xe] 6s2

Discovered By: Sir Humphry Davy in 1808.

Common Use: Barium compounds can be consumed to improve contrast in x-ray imaging of the digestive system. (See Unit 9, Section 8.)

56 Ba 137.33

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72

Hf

Hafnium

178.49

Hafnium is a silvery ductile metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 4, Period: 6

Electron configuration: [Xe] 4f14 5d2 6s2

Discovered By: Dirk Coster and George de Hevesy in 1922.

Common Use: Hafnium is mostly used to produce control rods for nuclear reactors. Hafnium is also used in light bulb filaments, photographic flash bulbs, and in electronic components.

72 Hf 178.49

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73

Ta

Tantalum

180.95

Tantalum is a shiny, gray, dense metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 5, Period: 6

Electron configuration: [Xe] 4f14 5d3 6s2

Discovered By: Anders Gustaf Ekeberg in 1802.

Common Use: Tantalum is used to make surgical and dental instruments, and is used in the electronics industry for capacitors and high power resistors.

73 Ta 180.95

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74

W

Tungsten

183.84

Tungsten is a very hard, dense, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 6, Period: 6

Electron configuration: [Xe] 4f14 5d4 6s2

Discovered By: Juan José Elhuyar and Fausto Elhuyar in 1783.

Common Use: Tungsten and its alloys are used for filaments in older electric light bulbs. Tungsten carbide (WC or W2C) is extremely hard and is used to make drills and other equipment for the metal working and mining industries. (See Unit 13 video.)

74 W 183.84

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75

Re

Rhenium

186.21

Rhenium is a dense, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 7, Period: 6

Electron configuration: [Xe] 4f14 5d5 6s2

Discovered By: Walter Noddack, Ida Tacke-Noddack, and Otto Berg in 1922.

Common Use: Rhenium is used in alloys for jet engines, and is used with platinum as catalysts in the production of lead-free, high-octane gasoline. (See Unit 4, Section 1 sidebar.)

75 Re 186.21

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76

Os

Osmium

190.23

Osmium is a hard, brittle, bluish-white transition metal, which is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 8, Period: 6

Electron configuration: [Xe] 4f14 5d6 6s2

Discovered By: Smithson Tennant in 1803.

Common Use: Osmium is the densest naturally occurring element. Osmium is used to produce very hard alloys with other metals of the platinum group and used for electrical contacts, fountain pen tips, and needles.

76 Os 190.23

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77

Ir

Iridium

192.22

Iridium is a hard, brittle, dense metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 9, Period: 6

Electron configuration: [Xe] 4f14 5d7 6s2

Discovered By: Smithson Tennant in 1803.

Common Use: Iridium is used to make heavy-duty electrical contacts, and is alloyed with many metals to improve them. Iridium was used in making the international standard kilogram: an alloy of 90% platinum and 10% iridium. Radioactive isotopes of iridium are used in radiation therapy for cancer treatment.

77 Ir 192.22

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78

Pt

Platinum

195.08

Platinum is a dense, soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 10, Period: 6

Electron configuration: [Xe] 4f14 5d9 6s1

Discovered By: Antonio de Ulloa in 1735.

Common Use: Platinum is a precious metal used in jewelry, dental work, for decoration, electrical contacts, and medical instruments. Platinum is also used as a catalytic converter in vehicles, allowing the complete combustion of unburned hydrocarbons from exhaust into carbon dioxide and water vapor. Platinum was the basis of the international standard kilogram: an alloy of 90% platinum and 10% iridium.

78 Pt 195.08

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79

Au

Gold

196.97

Gold is a soft, yellow metal that is solid at room temperature.

State: solid at standard conditions

Type: transition metal, Group: 11, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s1

Discovered By: People in ancient times.

Common Use: Gold is widely used in jewelry and coins, decoration, and in dental work as crowns. Gold is also used as a radiation reflector for satellites and astronaut helmet visors. (See Unit 3, Section 3.)

79 Au 196.97

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80

Hg

Mercury

200.59

Mercury is a dense, silvery-white metal that is liquid at room temperature.

State: liquid at standard conditions

Type: transition metal, Group: 12, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2

Discovered By: Ancient Chinese and Indians in approximately 1500 BCE.

Common Use: Mercury is used in instruments for measuring the pressure of gases and liquids, as well as in thermometers to measure temperature. It is also used in mercury-vapor lamps, which are used for street lighting, sun lamps, and as UV lights (black lights). (See Unit 1, Section 6.)

80 Hg 200.59

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81

Tl

Thallium

204.38

Thallium is a soft, malleable low-melting, silvery metal that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 13, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2 6p1

Discovered By: William Crookes in 1861.

Common Use: Thallium compounds are used to create photocells, and to make special optical glass that has a high index of refraction.

81 Tl 204.38

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82

Pb

Lead

207.2

Lead is a soft, dense, bluish-gray metal that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 14, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2 6p2

Discovered By: People in ancient times.

Common Use: Lead is used in construction, lead-acid batteries, bullets, weights, electrical solder, and as a shield for radiation. The use of lead in plumbing, fuel and paints has been greatly reduced because of health and environmental concerns. (See Unit 6, Section 6.)

82 Pb 207.2

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83

Bi

Bismuth

208.98

Bismuth is a crystalline, brittle metal that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 15, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2 6p3

Discovered By: Claude François Geoffroy in 1763.

Common Use: Bismuth compounds are used in cosmetics, medicine, low-melting alloys, fire detectors and extinguishers, and as a replacement for lead in shot and bullets.

83 Bi 208.98

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84

Po

Polonium

(209)

Polonium is a silvery-gray, radioactive metalloid that is solid at room temperature.

State: solid at standard conditions

Type: post-transition metal, Group: 16, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2 6p4

Discovered By: Marie Curie and Pierre Curie in 1898.

Common Use: Polonium was once used as a heat source in space equipment, and sealed inside anti-static brushes to eliminate dust on photographic film. (See Unit 12, Section 6.)

84 Po (209)

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85

At

Astatine

(210)

Astatine is an extremely radioactive solid at room temperature.

State: solid at standard conditions

Type: halogen, Group: 17, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2 6p5

Discovered By: Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè in 1940.

Common Use: Astatine is sometimes used nuclear medicine, such as in cancer treatment.

85 At (210)

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86

Rn

Radon

(222)

Radon is a radioactive, colorless, odorless gas under standard conditions.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 6

Electron configuration: [Xe] 4f14 5d10 6s2 6p6

Discovered By: Friedrich Ernst Dorn in 1898.

Common Use: Radon was once used for treating cancer by radiotherapy, and safer treatments are now available. (See Unit 12, Section 8 sidebar.)

86 Rn (222)

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87

Fr

Francium

(223)

Francium is a heavy radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: alkali metal, Group: 1, Period: 7

Electron configuration: [Rn] 7s1

Discovered By: Marguerite Perey in 1939.

Common Use: Francium is very rare and only has a half-life of 22 minutes, so it is used for research purposes only.

87 Fr (223)

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88

Ra

Radium

(226.03)

Radium is a silvery-white metal that is solid at room temperature

State: solid at standard conditions

Type: alkaline earth metal, Group: 2, Period: 7

Electron configuration: [Rn] 7s2

Discovered By: Marie Curie and Pierre Curie in 1898.

Common Use: Radium was once used to make luminous paints, which is now considered too dangerous. Radium chloride was used to produce radon gas for cancer treatment, though safer options are now available. (See Unit 3, Section 3.)

88 Ra (226.03)

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104

Rf

Rutherfordium

(267)

Rutherfordium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 4, Period: 7

Electron configuration: [Rn] 5f14 6d2 7s2

Discovered By: The Joint Institute for Nuclear Research in 1964.

Common Use: Rutherfordium is only used for research purposes.

104 Rf (267)

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105

Db

Dubnium

(268)

Dubnium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 5, Period: 7

Electron configuration: [Rn] 5f14 6d3 7s2

Discovered By: The Joint Institute for Nuclear Research in 1968.

Common Use: Dubnium is only used for research purposes.

105 Db (268)

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106

Sg

Seaborgium

(269)

Seaborgium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 6, Period: 7

Electron configuration: [Rn] 5f14 6d4 7s2

Discovered By: The Lawrence Berkeley National Laboratory in 1974.

Common Use: Seaborgium is only used for research purposes. (See Unit 4 video.)

106 Sg (269)

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107

Bh

Bohrium

(270)

Bohrium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 7, Period: 7

Electron configuration: [Rn] 5f14 6d5 7s2

Discovered By: The Institute for Heavy Ion Research in 1981.

Common Use: Bohrium is only used for research purposes.

107 Bh (270)

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108

Hs

Hassium

(269)

Hassium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 8, Period: 7

Electron configuration: [Rn] 5f14 6d6 7s2

Discovered By: The Institute for Heavy Ion Research in 1984.

Common Use: Hassium is only used for research purposes.

108 Hs (269)

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109

Mt

Meitnerium

(278)

Meitnerium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 9, Period: 7

Electron configuration: [Rn] 5f14 6d7 7s2

Discovered By: The Institute for Heavy Ion Research in 1982.

Common Use: Meitnerium is only used for research purposes.

109 Mt (278)

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110

Ds

Darmstadtium

(281)

Darmstadtium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 10, Period: 7

Electron configuration: [Rn] 5f14 6d8 7s2

Discovered By: The Institute for Heavy Ion Research in 1994.

Common Use: Darmstadtium is only used for research purposes.

110 Ds (281)

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111

Rg

Roentgenium

(281)

Roentgenium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 11, Period: 7

Electron configuration: [Rn] 5f14 6d9 7s2

Discovered By: The Institute for Heavy Ion Research in 1994.

Common Use: Roentgenium is only used for research purposes.

111 Rg (281)

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112

Cn

Copernicium

(285)

Copernicium is a highly radioactive metal, of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: transition metal, Group: 12, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2

Discovered By: The Institute for Heavy Ion Research in 1994.

Common Use: Copernicium is only used for research purposes.

112 Cn (285)

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113

Uut

Ununtrium

(286)

Ununtrium is a highly radioactive metal, of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: post-transition metal, Group: 13, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2 7p1

Discovered By: The synthesis of Ununtrium was reported by the Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory in 2003, however IUPAC has concluded that these results do not meet the criteria for discovery.

Common Use: Ununtrium is a synthetic radioactive metal that is of research interest only.

113 Uut (286)

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114

Fl

Flerovium

(289)

Flerovium is a highly radioactive metal, of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: post-transition metal, Group: 14, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2 7p2

Discovered By: The Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory in 1999.

Common Use: Flerovium is a synthetic radioactive metal that is of research interest only. (See Unit 4, Section 3.)

114 Fl (289)

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115

Uup

Ununpentium

(288)

A highly radioactive metal, of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: post-transition metal, Group: 15, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2 7p5

Discovered By: The Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory reported the discovery in 2003, however IUPAC has since concluded that these results do not meet the criteria for discovery.

Common Use: Ununpentium is of research interest only.

115 Uup (288)

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116

Lv

Livermorium

(293)

Livermorium is a highly radioactive metal, of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: post-transition metal, Group: 16, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2 7p4

Discovered By: The Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory in 2000.

Common Use: Livermorium is a synthetic radioactive metal that is of research interest only. (See Unit 4, Section 3.)

116 Lv (293)

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117

Uus

Ununseptium

(294)

Ununseptium is a highly radioactive metal, of which only a few atoms have ever been made.

State: solid at standard conditions

Type: halogen, Group: 17, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2 7p5

Discovered By: The synthesis of Ununseptium was reported by the Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory in 2010, however IUPAC has concluded that these results do not meet the criteria for discovery.

Common Use: Ununseptium is a synthetic radioactive metal that is of research interest only.

117 Uus (294)

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118

Uuo

Ununoctium

(294)

Ununoctium is a highly radioactive metal, of which only a few atoms have ever been made.

State: gas at standard conditions

Type: noble gas, Group: 18, Period: 7

Electron configuration: [Rn] 5f14 6d10 7s2 7p6

Discovered By: The synthesis of Ununoctium was reported by the Joint Institute for Nuclear Research and Lawrence Livermore National Laboratory in 2002, however IUPAC has concluded that these results do not meet the criteria for discovery.

Common Use: Ununoctium is a synthetic radioactive metal that is of research interest only.

118 Uuo (294)

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57

La

Lanthanum

138.91

Lanthanum is a silvery-white soft metal, that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 5d1 6s2

Discovered By: Carl Gustaf Mosander in 1838.

Common Use: Lanthanum is used in rechargeable batteries for hybrid cars.

57 La 138.91

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58

Ce

Cerium

140.12

Cerium is soft gray metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f1 5d1 6s2

Discovered By: Jöns Jakob Berzelius and Wilhelm Hisinger, and independently by Martin Heinrich Klaproth in 1803.

Common Use: Cerium compounds are used as a catalytic converter to reduce carbon monoxide emissions from automobiles. Cerium is also used in diesel fuel to improve engine performance, and is used in self-cleaning ovens.

58 Ce 140.12

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59

Pr

Praseodymium

140.91

Praseodymium is a soft, malleable, ductile, silvery metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f3 6s2

Discovered By: Carl Auer von Welsbach in 1885.

Common Use: Praseodymium is used in alloys, as flints for pocket lighters and to color glass an intense yellow. In particular, praseodymium is used to produce yellow protective visor glass used by welders and glassmakers.

59 Pr 140.91

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60

Nd

Neodymium

144.24

Neodymium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f4 6s2

Discovered By: Carl Auer von Welsbach in 1885.

Common Use: Neodymium is used to create powerful permanent magnets, which are used in computers, cell phones, medical equipment, motors, and wind turbines.

60 Nd 144.24

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61

Pm

Promethium

(145)

Promethium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f5 6s2

Discovered By: Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin, and Harold G. Richter in 1945.

Common Use: Promethium is used in atomic batteries for spacecraft and guided missiles, and can also be used to make batteries for watches and radios.

61 Pm (145)

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62

Sm

Samarium

150.36

Samarium is a bright silvery white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f6 6s2

Discovered By: Lecoq de Boisbaudran in 1879.

Common Use: Samarium is mainly used to create robust samarium-cobalt alloy magnets for small motors, headphones, and pickups for electric guitars. Because these magnets are highly resistant to demagnetization even at very high temperatures, they are also used in military weapons.

62 Sm 150.36

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63

Eu

Europium

151.96

Europium is a soft silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f7 6s2

Discovered By: Eugène-Anatole Demarçay in 1896.

Common Use: Europium is one of the elements used to create the red color in on some high definition screens, in fluorescent lamps, and in early color television tubes.

63 Eu 151.96

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64

Gd

Gadolinium

157.25

Gadolinium is a bright, soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f7 5d1 6s2

Discovered By: Jean Charles Galissard de Marignac in 1880.

Common Use: Gadolinium compounds are used in magnetic resonance imaging (MRI) machines, particularly in diagnosing cancerous tumors. Gadolinium is also one of the elements used to create the green color in early color televisions.

64 Gd 157.25

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65

Tb

Terbium

158.93

Terbium is a soft, malleable, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f9 6s2

Discovered By: Carl Gustaf Mosander in 1842.

Common Use: Terbium is one of the elements used to create the green color on some high definition screens, in fluorescent lamps, and in early color television tubes.

65 Tb 158.93

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66

Dy

Dysprosium

162.50

Dysprosium is a bright, soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f10 6s2

Discovered By: Lecoq de Boisbaudran in 1886.

Common Use: Dysprosium is used to create strong magnets, and is used to make control rods in nuclear reactors. Dysprosium is also used in CDs and hard drives, and in making laser materials and commercial lighting.

66 Dy 162.50

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67

Ho

Holmium

164.93

Holmium is a bright, soft, silvery-white, metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f11 6s2

Discovered By: Marc Delafontaine and Jacques-Louis Soret, and independently by Per Teodor Cleve in 1878.

Common Use: Holmium is used in nuclear reactors to keep chain reactions under control. It is also used in the production of magnets, and in solid-state lasers for non-invasive medical procedures.

67 Ho 164.93

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68

Er

Erbium

167.26

Erbium is a bright, soft, malleable, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f12 6s2

Discovered By: Carl Gustaf Mosander in 1842.

Common Use: Erbium is used in nuclear reactor control rods, and in photographic filters to absorb infrared light.

68 Er 167.26

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69

Tm

Thulium

168.93

Thulium is a bright, soft, silvery-gray metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f13 6s2

Discovered By: Per Teodor Cleve in 1879.

Common Use: Thulium is used to make lightweight, portable X-ray machines for medical use. It glows blue under UV light, and so is added to euro banknotes to combat counterfeiting.

69 Tm 168.93

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70

Yb

Ytterbium

173.05

Ytterbium is a bright, soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f14 6s2

Discovered By: Jean Charles Galissard de Marignac in 1878.

Common Use: Ytterbium can be used as a radiation source in portable X-ray machines. Ytterbium's electrical resistance increases under physical stress, so it's also used in instruments that monitor earthquakes and underground explosions.

70 Yb 173.05

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71

Lu

Lutetium

174.97

Lutetium is a silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: lanthanide, Group: n/a, Period: 6

Electron configuration: [Xe] 4f14 5d1 6s2

Discovered By: Georges Urbain, independently by Carl Auer von Welsbach, and independently by Charles James in 1907.

Common Use: Lutetium isotopes are used in cancer therapy, and to calculate the age of meteorites.

71 Lu 174.97

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89

Ac

Actinium

(227)

Actinium is a soft, silvery-white, radioactive, metallic element that is solid at room temperature, and glows in the dark.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 6d1 7s2

Discovered By: André-Louis Debierne in 1899.

Common Use: Actinium is rarely used outside research.

89 Ac (227)

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90

Th

Thorium

232.04

Thorium is a radioactive, bright, soft, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 6d2 7s2

Discovered By: Jöns Jakob Berzelius in 1829.

Common Use: Thorium dioxide is used in heat resistant ceramics, and is used to produce special optical glass. Thorium alloys are used for aircraft engines.

90 Th 232.04

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91

Pa

Protactinium

231.04

Protactinium is a dense, silvery-gray, radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f2 6d1 7s2

Discovered By: William Crookes in 1900.

Common Use: Protactinium is mainly used for research purposes.

91 Pa 231.04

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92

U

Uranium

238.03

Uranium is a dense, radioactive, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f3 6d1 7s2

Discovered By: Martin Heinrich Klaproth in 1789.

Common Use: Uranium is used as fuel for nuclear power plants. (See Unit 12, Section 7.)

92 U 238.03

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93

Np

Neptunium

(237)

Neptunium is a silvery radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f4 6d1 7s2

Discovered By: Edwin McMillan and Philip H. Abelson in 1940.

Common Use: Neptunium is mainly used for research purposes.

93 Np (237)

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94

Pu

Plutonium

(224)

Plutonium is a silvery-white radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f6 7s2

Discovered By: Glenn T. Seaborg, Arthur Wahl, Joseph W. Kennedy and Edwin McMillan in 1940.

Common Use: Plutonium is used as a long-lasting power and heat source for space probes, and in nuclear bombs and reactors. (See Unit 12, Section 11.)

94 Pu (224)

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95

Am

Americium

(243)

Americium is a silvery-white radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f7 7s2

Discovered By: Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, and Albert Ghiorso in 1944.

Common Use: Americium is used in very small amounts in household smoke detectors, and as a portable source of gamma rays for medical use.

95 Am (243)

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96

Cm

Curium

(247)

Curium is a hard, radioactive, silvery-white metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f7 6d1 7s2

Discovered By: Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944.

Common Use: Curium is used in scientific instruments that measure the abundance of chemical elements in rocks and soil on Mars.

96 Cm (247)

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97

Bk

Berkelium

(247)

Berkelium is a silvery-white, radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f9 7s2

Discovered By: Stanley G. Thompson, Glenn T. Seaborg, and Albert Ghiorso in 1949.

Common Use: Berkelium is used mainly for research purposes.

97 Bk (247)

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98

Cf

Californium

(251)

Californium is a soft, silvery-white, radioactive metal that is solid at room temperature.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f10 7s2

Discovered By: Stanley G. Thompson, Kenneth Street, Jr., Albert Ghiorso, and Glenn T. Seaborg in 1950.

Common Use: Californium provides neutrons for the start-up of nuclear reactors. It is also used to treat certain kinds of cancer.

98 Cf (251)

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99

Es

Einsteinium

(252)

Einsteinium is a synthetic radioactive metal that has only been produced in very small amounts.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f11 7s2

Discovered By: The Lawrence Berkeley National Laboratory in 1952.

Common Use: Einsteinium is mainly used for research purposes.

99 Es (252)

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100

Fm

Fermium

(257)

Fermium is a synthetic radioactive metal and has only been produced in tiny amounts.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f12 7s2

Discovered By: The Lawrence Berkeley National Laboratory in 1952.

Common Use: Fermium is only used for research purposes.

100 Fm (257)

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101

Md

Mendelevium

(258)

Mendelevium is a synthetic radioactive metal that has only been produced in tiny amounts.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f13 7s2

Discovered By: The Lawrence Berkeley National Laboratory in 1955.

Common Use: Mendelevium is only used for research purposes.

101 Md (258)

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102

No

Nobelium

(259)

Nobelium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f14 7s2

Discovered By: The Joint Institute for Nuclear Research in 1966.

Common Use: Nobelium is only used for research purposes.

102 No (259)

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103

Lr

Lawrencium

(262)

Lawrencium is a synthetic radioactive metal of which only a few atoms have ever been made.

State: expected to be a solid at standard conditions

Type: actinide, Group: n/a, Period: 7

Electron configuration: [Rn] 5f14 7s2 7p1

Discovered By: The Lawrence Berkeley National Laboratory in 1961.

Common Use: Lawrencium is only used for research purposes.

103 Lr (262)

Groups

Elements beginning with "Uu" have not been identified.

Atomic weights in parentheses have not been verified.