Lithium (Li): Bohr Model, Protons, Neutrons & Electrons
Lithium is element number 3, an alkali metal in group 1, period 2. Its atom has 3 protons, 4 neutrons and 3 electrons arranged in 2 shells: 2, 1.
Protons, neutrons and electrons in lithium
The atomic number of lithium is 3, so every lithium atom has 3 protons. A neutral atom has the same number of electrons, 3. The number of neutrons depends on the isotope: neutrons = mass number − atomic number. For lithium-7, that is 7 − 3 = 4 neutrons. Lithium has 2 stable isotopes, with 3, 4 neutrons.
How to draw the Bohr model of lithium
- Draw the nucleus and write 3 p⁺ and 4 n⁰ inside it.
- Draw the first shell and put 2 electrons on it (the first shell holds at most 2).
- Draw the second shell and put 1 electron on it.
- Check: 2 + 1 = 3 electrons, the same as the number of protons.
Electron configuration
The electron configuration of lithium is [He] 2s¹. Its 1 outer electron decides how it reacts: it tends to lose it, forming Li⁺ ions.
Key facts about lithium
| Symbol | Li |
|---|---|
| Atomic number | 3 |
| Relative atomic mass | 6.94 |
| Group · period · block | group 1 · period 2 · s-block |
| Type | Alkali Metal |
| State at 25 °C | solid |
| Electron shells | 2, 1 |
| Electron configuration | [He] 2s¹ |
| Valence electrons | 1 |
| Common ion | Li⁺ |
| Electronegativity (Pauling) | 0.98 |
| First ionisation energy | 5.39 eV (520 kJ/mol) |
| Atomic radius (empirical) | 145 pm |
Where lithium sits on the periodic table
Frequently asked questions
How many protons, neutrons and electrons does lithium have?
Lithium has 3 protons and 3 electrons (atomic number 3). Its most common isotope, lithium-7, has 7 − 3 = 4 neutrons.
What is the electron configuration of lithium?
[He] 2s¹. In shells that is 2, 1.
How many valence electrons does lithium have?
1. Lithium is in group 1, and its outer shell holds 1 electron.
Where is lithium on the periodic table?
In group 1, period 2, in the s-block. It is an alkali metal.
