Sodium (Na)
Element 11 · Alkali metal · atomic mass 22.99 u · group 1, period 3
Electron shells: 2, 8, 1
Sodium is a soft, highly reactive alkali metal that must be stored under oil to keep it from the air. Its ion is essential to nerve signalling in every animal.
Every nerve impulse you have ever had was carried by sodium ions crossing a cell membrane.
- Atomic number
- 11
- Atomic mass
- 22.99 u
- Electron configuration
- [Ne] 3s¹
- Group · period · block
- 1 · 3 · s
- Oxidation states
- +1
- Electronegativity
- 0.93 (Pauling)
- Melting point
- 97.8 °C
- Boiling point
- 883 °C
- Density
- 0.97 g/cm³
- State at 20 °C
- Solid
- Appearance
- Soft, silvery-white metal
- Discovered
- Humphry Davy, 1807
11 protons, and 11 electrons when neutral
IUPAC standard atomic weight
Alkali metals
What Sodium is used for
- Table salt and food processing
- Sodium-vapour street lighting
- Coolant in fast-breeder reactors
- Producing other chemicals
Atomic structure of Sodium
A neutral sodium atom has 11 protons and 11 electrons. Its most common isotope carries about 12 neutrons, which is where the mass number 23 comes from. Change the neutron count and you have a different isotope of sodium; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 1. In orbital notation that is [Ne] 3s¹, leaving 1 valence electron in the outer shell — the ones that do the chemistry.
3D electron orbitals
See where Sodium's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Sodium sits in the periodic table
Group 1 metals with a single outer electron. Soft, low-melting and so reactive they are stored under oil — reactivity increases as you go down the group.
Discovery and naming
Sodium was discovered by Humphry Davy in 1807. Its name comes from English soda; symbol from Latin natrium, which is also why its symbol (Na) does not match its English name.
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Sodium?
The standard atomic weight of Sodium is 22.99 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Sodium have?
Sodium has 11 protons, because the atomic number is the proton count and that is what makes an atom Sodium at all. A neutral Sodium atom has the same number of electrons, 11. The neutron count varies by isotope; the most common one has about 12, since 23 − 11 = 12.
What is the electron configuration of Sodium?
The electron configuration of Sodium is [Ne] 3s¹. Its electrons are arranged 2, 8, 1 across 3 shells.
Is Sodium a metal?
Yes. Sodium is classified as a alkali metal, on the left side of the table.
What group and period is Sodium in?
Sodium is in group 1 (the alkali metals), period 3, in the s-block. The group is its column and the period is its row.
What is the charge of Sodium?
Sodium most commonly forms a 1+ ion. It has 1 electron in its outer shell and loses it readily, which is what the group number tells you.
What is the melting point of Sodium?
Sodium melts at 97.8 °C and boils at 883 °C. That puts it in the solids at everyday temperatures.
What is Sodium used for?
Table salt and food processing, Sodium-vapour street lighting, Coolant in fast-breeder reactors, Producing other chemicals. Sodium is a soft, highly reactive alkali metal that must be stored under oil to keep it from the air.
Who discovered Sodium, and where does its name come from?
Sodium (Na) was discovered by Humphry Davy in 1807. The name comes from English soda; symbol from Latin natrium.