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.

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Hydrogen Element on the periodic table

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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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Low Angle View Of Cropped Hand Holding Colorful Helium Balloons Against Sky

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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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An employee holds processed 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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Piece of blue Beryl mineral

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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 magnets

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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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Full Frame Shot Of Coal

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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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iquid nitrogen being poured into a canister

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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] 2s​2 2p3

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

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Close up of Oxygen tubes for diving

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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 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 glowing sign on the wall with moss

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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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salt on a wooden spoon

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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 ribbon

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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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Rows of aluminum coils sit on the floor of a manufacturing facility

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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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Close-up of the surface of a solar (photovoltaic) cell
The cell is made from silicon (blue), a semi-conductor.


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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High speed flash shot of match igniting
Red phosphorus can be found in safety matches.

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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 and salt deposits at Dallol hydrothermal hot springs

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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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Measurement of chlorine and PH of a poo
Measuring the chlorine level and PH of a pool.

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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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Masked worker argon welding

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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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Texture of granules and crystals of 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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Pouring milk in the glass on the background of nature

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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