Sodium (Na)
Sodium is element 11, an alkali metal in group 1, period 3. A neutral atom has 11 protons, 12 neutrons and 11 electrons, 1 of them valence electrons.
Alkali metal- Atomic number
- 11
- Atomic mass
- 22.99 u
- Valence electrons
- 1
- Protons · neutrons
- 11 · 12
- Electrons per shell
- 2, 8, 1
- At room temperature
- solid
Bohr model of sodium
The Bohr model draws sodium as a nucleus of 11 protons and 12 neutrons, with its 11 electrons on 3 circular shells: 2 in shell 1, 8 in shell 2, 1 in shell 3. Press Build the atom to watch the shells fill from the inside out. The outer ring (the M shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of sodium
1s² 2s² 2p⁶ 3s¹
Short form (noble gas notation): [Ne] 3s¹. The [Ne] stands for the electrons of neon, the noble gas before it.
How many valence electrons does sodium have?
Sodium has 1 valence electron.
Sodium is in group 1, so it has 1 valence electron. It tends to lose that electron and form a +1 ion.
Protons, neutrons and electrons
| Protons | 11 | equal to the atomic number |
|---|---|---|
| Electrons | 11 | equal to the protons in a neutral atom |
| Neutrons | 12 | mass number 23 − 11 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Sodium properties
| Symbol | Na |
|---|---|
| Category | Alkali metal |
| Group · period · block | 1 · 3 · s |
| Atomic mass | 22.99 u |
| State at 25 °C | solid |
| Melting point | 370.9 K (97.8 °C, 208 °F) |
| Boiling point | 1,156 K (883 °C, 1,620 °F) |
| Density | 0.97 g/cm³ |
| Electronegativity (Pauling) | 0.93 |
| Atomic radius | 227 pm |
| First ionization energy | 5.139 eV |
| Electron affinity | 0.548 eV |
| Oxidation states | +1 |
| Common ion charge | +1 |
| Discovered | 1807 by Humphry Davy |
Where sodium sits on the periodic table
Group 1: Hydrogen, Lithium, Potassium, Rubidium, Cesium, Francium.
Questions about sodium
How many valence electrons does sodium have?
Sodium has 1 valence electron.
How many protons, neutrons and electrons does sodium have?
A neutral sodium atom has 11 protons and 11 electrons. Its most common form has about 12 neutrons (mass number 23 − 11 protons).
What is the electron configuration of sodium?
1s² 2s² 2p⁶ 3s¹, written in short form as [Ne] 3s¹.
What does the Bohr model of sodium look like?
A nucleus of 11 protons and 12 neutrons, circled by 3 electron shells holding 2, 8, 1 electrons.
What is the atomic number of sodium?
11. The atomic number is the number of protons in the nucleus, and it is what makes an atom sodium.