Sodium (Na): electron configuration, atomic mass and facts
Sodium (Na) is element 11 of the periodic table, an alkali metal in period 3, group 1. Its electron configuration is [Ne] 3s1, with electrons arranged in shells 2, 8, 1, and its standard atomic weight is 22.99 u.
💡 A soft metal you can cut with a knife. It fizzes and melts on water and burns golden-yellow.
▶ Watch Sodium’s electrons orbit in the interactive periodic tableSodium at a glance
| Symbol | Na |
|---|---|
| Atomic number | 11 |
| Atomic mass | 22.99 u |
| Category | Alkali metal |
| Group | 1 |
| Period | 3 |
| Block | s-block |
| Electron configuration | 1s2 2s2 2p6 3s1 |
| Noble-gas shorthand | [Ne] 3s1 |
| Electrons per shell | 2, 8, 1 |
| Outer-shell electrons | 1 |
| Electronegativity (Pauling) | 0.93 |
| State at 20 °C | solid |
| Flame test colour | intense golden-yellow |
Experiments with sodium
🧪 Acid–base titration
Find the end-point of HCl vs NaOH with phenolphthalein and plot the titration curve.
⚪ Amphoteric hydroxides
Aluminium hydroxide precipitates, then dissolves again in excess NaOH.
🧊 Hot & cold packs
Dissolving salts can absorb heat (NH₄NO₃) or release it (CaCl₂, NaOH).
🌋 Baking-soda volcano
Vinegar + bicarbonate + washing-up liquid produce a frothy eruption.
Where is Sodium on the periodic table?
Sodium is in period 3, group 1, in the s-block. The period number matches its 3 electron shells, and the block names the subshell its last electrons fill. In the same group, Lithium sits directly above it and Potassium sits directly below it. Elements in one group have the same number of outer-shell electrons (1 here), which is why they react in similar ways.
How to work out the electron configuration of Sodium
Put 11 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s¹ (11). In shorthand, [Ne] stands for the 10 electrons of neon, giving [Ne] 3s¹.
How electronegative is Sodium?
Sodium has a Pauling electronegativity of 0.93, ranking 94 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Sodium in the virtual lab
Faradium’s chemistry workbench includes these chemicals that contain sodium: Sodium (small piece), Sodium carbonate, Baking soda, Sodium chloride, Sodium hydroxide pellets, Sodium hydroxide, Sodium hydroxide 0.1 M, Brine (saturated), Sodium bromide, Sodium hydrogencarbonate, Sodium sulfate, Sodium sulfide, Sodium sulfite, Sodium thiosulfate. Open the Chemistry Lab to experiment with them.
Frequently asked questions
What is the electron configuration of Sodium?
The electron configuration of Sodium (Na) is 1s2 2s2 2p6 3s1. In noble-gas shorthand it is written [Ne] 3s1.
How many electrons does Sodium have in each shell?
Sodium has 11 electrons arranged in shells as 2, 8, 1. It has 1 electron in its outer shell.
What is the atomic mass of Sodium?
The standard atomic weight of Sodium is 22.99 u, so one mole of Sodium atoms has a mass of about 22.99 g.
Is Sodium a metal?
Yes. Sodium is an alkali metal.
Explore nearby elements
More alkali metals: Lithium, Potassium, Rubidium, Caesium, Francium. See all elements on the periodic table.