First 20 Elements of the Periodic Table

Element Names, Symbols, Atomic Numbers, and Facts

Get essential facts about the first 20 elements, all in one convenient place, including the name, atomic number, atomic mass, element symbol, group, and electron configuration. If you need detailed facts about these elements or any of the higher numbered ones, start with the clickable periodic table.

01
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Hydrogen is the first element on the periodic table.
Hydrogen is the first element on the periodic table. William Andrew / Getty Images

Hydrogen is a nonmetallic, colorless gas under ordinary conditions. It becomes an alkali metal under extreme pressure.

Atomic Number: 1

Symbol: H

Atomic Mass: 1.008

Electron Configuration: 1s1

Group: group 1, s-block, nonmetal More »

02
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Helium is the second element on the periodic table.
Helium is the second element on the periodic table. Science Picture Co / Getty Images

Helium is a light, colorless gas that forms a colorless liquid.

Atomic Number: 2

Symbol: He

Atomic Mass: 4.002602(2)

Electron Configuration: 1s2

Group: group 18, s-block, noble gas More »

03
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Lithium is the lightest metal on the periodic table.
Lithium is the lightest metal on the periodic table. Science Picture Co / Getty Images

Lithium is a reactive silver metal.

Atomic Number: 3

Symbol: Li

Atomic Mass: 6.94 (6.938–6.997)

Electron Configuration: [He] 2s1

Group: group 1, s-block, alkali metal More »

04
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Beryllium, atomic number 4. Beryllium is a lightweight, corrosion-resistant metallic element.
Beryllium, atomic number 4. Beryllium is a lightweight, corrosion-resistant metallic element. Lester V. Bergman / Getty Images

Beryllium is a shiny gray-white metal.

Atomic Number: 4

Symbol: Be

Atomic Mass: 9.0121831(5)

Electron Configuration: [He] 2s2

Group: group 2, s-block, alkaline earth metal More »

05
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Boron, a soft, amorphous or crystalline nonmetallic element, used in flares and nuclear reactor control rods.
Boron, a soft, amorphous or crystalline nonmetallic element, used in flares and nuclear reactor control rods. Lester V. Bergman / Getty Images

Boron is a gray solid with a metallic luster.

Atomic Number: 5

Symbol: B

Atomic Mass: 10.81 (10.806–10.821)

Electron Configuration: [He] 2s2 2p1

Group: group 13, p-block, metalloid More »

06
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Forms of carbon including a coal, charcoal, graphite and diamonds.
Forms of carbon including a coal, charcoal, graphite and diamonds. Dave King / Getty Images

Carbon takes several forms. It's usually a gray or black solid, although diamonds may be colorless.

Atomic Number: 6

Symbol: C

Atomic Mass: 12.011 (12.0096–12.0116)

Electron Configuration: [He] 2s2 2p2

Group: group 14, p-block, usually a nonmetal although sometimes considered a metalloid More »

07
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Nitrogen (Chemical Element)
Nitrogen (Chemical Element). Science Picture Co / Getty Images

Nitrogen is a colorless gas under ordinary conditions. It cools to form colorless liquid and solid forms.

Atomic Number: 7

Symbol: N

Atomic Mass: 14.007

Electron Configuration: [He] 2s2 2p3

Group: group 15 (pnictogens), p-block, nonmetal More »

08
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Oxygen (Chemical Element)
Oxygen (Chemical Element). Science Picture Co / Getty Images

Oxygen is a colorless gas. Its liquid is blue. Solid oxygen may be any of several colors, including red, black, and metallic.

Atomic Number: 8

Symbol: O

Atomic Mass: 15.999 or 16.00

Electron Configuration: [He] 2s2 2p4

Group: group 16 (chalcogens), p-block, nonmetal More »

09
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Fluorine (Chemical Element)
Fluorine (Chemical Element). Science Picture Co / Getty Images

Fluorine is a pale yellow gas and liquid and bright yellow solid. The solid may be either opaque or translucent.

Atomic Number: 9

Symbol: F

Atomic Mass: 18.998403163(6)

Electron Configuration: [He] 2s2 2p5

Group: group 17, p-block, halogen More »

10
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Neon (Chemical Element)
Neon (Chemical Element). Science Picture Co / Getty Images

Neon is a colorless gas that emits a characteristic orange-red glow when excited in an electric field.

Atomic Number: 10

Symbol: Ne

Atomic Mass: 20.1797(6)

Electron Configuration: [He] 2s2 2p6

Group: group 18, p-block, noble gas More »

11
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Sodium (Chemical Element)
Sodium (Chemical Element). Science Picture Co / Getty Images

Sodium is a soft, silvery-white metal.

Atomic Number: 11

Symbol: Na

Atomic Mass: 22.98976928(2)

Electron Configuration: [Ne] 3s1

Group: group 1, s-block, alkali metal More »

12
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Magnesium, metal fern-like crystallization from melt and Mg scrap (Blue background).Magnesium is a chemical element with the symbol Mg and atomic number 12.
Magnesium, metal fern-like crystallization from melt and Mg scrap (Blue background).Magnesium is a chemical element with the symbol Mg and atomic number 12. Lester V. Bergman / Getty Images

Magnesium is a shiny gray metal.

Atomic Number: 12

Symbol: Mg

Atomic Mass: 24.305

Electron Configuration: [Ne] 3s2

Group: group 2, s-block, alkaline earth metal More »

13
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Pure aluminum chemical element.
Pure aluminum chemical element. Kerstin Waurick / Getty Images

 Aluminum is a soft, silver-colored, nonmagnetic metal.

Atomic Number: 13

Symbol: Al

Atomic Mass: 26.9815385(7)

Electron Configuration: [Ne] 3s2 3p1

Group: group 13, p-block, considered a post-transition metal or sometimes a metalloid More »

14
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Silicon (Chemical Element)
Silicon (Chemical Element). Science Picture Co / Getty Images

 Silicon is a hard, blue-gray crystalline solid that has a metallic luster.

Atomic Number: 14

Symbol: Si

Atomic Mass: 28.085

Electron Configuration: [Ne] 3s2 3p2

Group: group 14 (carbon group), p-block, metalloid More »

15
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Phosphorus (Chemical Element)
Phosphorus (Chemical Element). Science Picture Co / Getty Images

 Phosphorus is a solid under ordinary conditions, but it takes several forms. The most common are white phosphorus and red phosphorus.

Atomic Number: 15

Symbol: P

Atomic Mass: 30.973761998(5)

Electron Configuration: [Ne] 3s2 3p3

Group: group 15 (pnictogens), p-block, usually considered a nonmetal, but sometimes a metalloid More »

16
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Native Sulfur
Native Sulfur. Scientifica / Getty Images

 Sulfur is a yellow solid.

Atomic Number: 16

Symbol: S

Atomic Mass: 32.06

Electron Configuration: [Ne] 3s2 3p4

Group: group 16 (chalcogens), p-block, nonmetal More »

17
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Chlorine (Chemical Element)
Chlorine (Chemical Element). Science Picture Co / Getty Images

Chlorine is a pale yellow-green gas under ordinary conditions. Its liquid form is bright yellow.

Atomic Number: 17

Symbol: Cl

Atomic Mass: 35.45

Electron Configuration: [Ne] 3s2 3p5

Group: group 17, p-block, halogen More »

18
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Argon (Chemical Element)
Argon (Chemical Element). Science Picture Co / Getty Images

Argon is a colorless gas, liquid, and solid. It emits a bright lilac-purple glow when excited in an electric field.

Atomic Number: 18

Symbol: Ar

Atomic Mass: 39.948(1)

Electron Configuration: [Ne] 3s2 3p6

Group: group 18, p-block, noble gas More »

19
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Potassium (Chemical Element)
Potassium (Chemical Element). Science Picture Co / Getty Images

Potassium is a reactive, silvery metal.

Atomic Number: 19

Symbol: K

Atomic Mass: 39.0983(1)

Electron Configuration: [Ar] 4s1

Group: group 1, s-block, alkali metal More »

20
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Calcium (Chemical Element)
Calcium (Chemical Element). Science Picture Co / Getty Images

Calcium is a dull silver metal with a faint yellowish cast.

Atomic Number: 20

Symbol: Ca

Atomic Mass: 40.078(4)

Electron Configuration: [Ar] 4s2

Group: group 2, s-block, alkaline earth metal More »