First 20 Elements of the Periodic Table

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.

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Hydrogen

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

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Helium

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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

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Lithium

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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

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Beryllium

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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

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Boron

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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

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Carbon

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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

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Nitrogen

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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

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Oxygen

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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

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Fluorine

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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

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Neon

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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

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Sodium

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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

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Magnesium

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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

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Aluminum

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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

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Silicon

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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

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Phosphorus

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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

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Sulfur

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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

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Chlorine

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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

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Argon

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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

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Potassium

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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

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Calcium

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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

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Helmenstine, Anne Marie, Ph.D. "First 20 Elements of the Periodic Table." ThoughtCo, Aug. 28, 2020, thoughtco.com/first-20-elements-of-the-periodic-table-4106644. Helmenstine, Anne Marie, Ph.D. (2020, August 28). First 20 Elements of the Periodic Table. Retrieved from https://www.thoughtco.com/first-20-elements-of-the-periodic-table-4106644 Helmenstine, Anne Marie, Ph.D. "First 20 Elements of the Periodic Table." ThoughtCo. https://www.thoughtco.com/first-20-elements-of-the-periodic-table-4106644 (accessed March 30, 2023).