Periodic Table of Elements

The first 20 elements organized by atomic number — IUPAC 2024.

Legend

Nonmetal

Noble Gas

Alkali Metal

Alkaline Earth

Metalloid

Halogen

Z	Symbol	Name	Mass (u)	Category	Config
1	H	Hydrogen	1.008	Nonmetal	`1s¹`
2	He	Helium	4.003	Noble gas	`1s²`
3	Li	Lithium	6.941	Alkali metal	`[He] 2s¹`
4	Be	Beryllium	9.012	Alkaline earth	`[He] 2s²`
5	B	Boron	10.81	Metalloid	`[He] 2s² 2p¹`
6	C	Carbon	12.01	Nonmetal	`[He] 2s² 2p²`
7	N	Nitrogen	14.01	Nonmetal	`[He] 2s² 2p³`
8	O	Oxygen	16.00	Nonmetal	`[He] 2s² 2p⁴`
9	F	Fluorine	19.00	Halogen	`[He] 2s² 2p⁵`
10	Ne	Neon	20.18	Noble gas	`[He] 2s² 2p⁶`
11	Na	Sodium	22.99	Alkali metal	`[Ne] 3s¹`
12	Mg	Magnesium	24.31	Alkaline earth	`[Ne] 3s²`
13	Al	Aluminium	26.98	Post-transition	`[Ne] 3s² 3p¹`
14	Si	Silicon	28.09	Metalloid	`[Ne] 3s² 3p²`
15	P	Phosphorus	30.97	Nonmetal	`[Ne] 3s² 3p³`
16	S	Sulfur	32.06	Nonmetal	`[Ne] 3s² 3p⁴`
17	Cl	Chlorine	35.45	Halogen	`[Ne] 3s² 3p⁵`
18	Ar	Argon	39.95	Noble gas	`[Ne] 3s² 3p⁶`
19	K	Potassium	39.10	Alkali metal	`[Ar] 4s¹`
20	Ca	Calcium	40.08	Alkaline earth	`[Ar] 4s²`

Period 1: 1s
Period 2: 2s 2p
Period 3: 3s 3p
Period 4: 4s 3d 4p
Period 5: 5s 4d 5p
Period 6: 6s 4f 5d 6p
Period 7: 7s 5f 6d 7p

Data from IUPAC Periodic Table of the Elements, 2024 edition.