Sodium
Sodium (Na) is an alkali metal with atomic number 11 and an atomic mass of 22.99. Its electron configuration is [Ne] 3s1, which gives it 1 valence electron.
Sodium key data
| Symbol | Na |
|---|---|
| Atomic number | 11 |
| Atomic mass (standard atomic weight) | 22.99 |
| Molar mass | 22.99 g/mol |
| Protons | 11 |
| Neutrons (most abundant isotope, sodium-23) | 12 |
| Electrons (neutral atom) | 11 |
| Valence electrons | 1 |
| Category | Alkali metal |
| Period | 3 |
| Group | 1 |
| Block | s-block |
| Noble gas notation | [Ne] 3s1 |
| Full electron configuration | 1s2 2s2 2p6 3s1 |
| Electrons per shell | 2, 8, 1 |
Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.
The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.
Measured properties of sodium
From PubChem, the US National Institutes of Health. Public domain.
| Melting point | 370.95 K (97.8 °C), 84th of 103 by melting point |
|---|---|
| Boiling point | 1156 K (882.85 °C), 71st of 93 by boiling point |
| Density | 0.97 g/cm³, 83rd of 96 by density |
| State at room temperature | Solid |
| Electronegativity | 0.93 (Pauling), 89th of 95 by electronegativity |
| Van der Waals radius | 227 pm, joint 30th of 99 by atomic radius |
| First ionisation energy | 5.139 eV (495.8 kJ/mol), 98th of 102 by first ionisation energy |
| Electron affinity | 0.548 eV (52.9 kJ/mol), 37th of 57 by electron affinity |
| Common oxidation states | +1 |
| Discovered | 1807 |
Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.
Sodium electron configuration
The full electron configuration of sodium is 1s2 2s2 2p6 3s1. With the noble-gas core collapsed it is [Ne] 3s1, and the outermost subshell is 3s1.
Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.
Mass of one sodium atom
A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.
Mass of one atom
- one atom = 22.99 / (6.02214076 × 10²³)
- = 3.8176 × 10⁻²³ g
Atoms in one gram
- atoms per gram = 6.02214076 × 10²³ / 22.99
- = 2.6195 × 10²² atoms
Sodium on the periodic table
Sodium is in period 3, group 1, in the s-block.
The other elements of group 1 are hydrogen, lithium, potassium, rubidium, caesium and francium.
The rest of period 3
- 12 Mg Magnesium
- 13 Al Aluminium
- 14 Si Silicon
- 15 P Phosphorus
- 16 S Sulfur
- 17 Cl Chlorine
- 18 Ar Argon