Lithium (Li)
Lithium is element 3, an alkali metal in group 1, period 2. A neutral atom has 3 protons, 4 neutrons and 3 electrons, 1 of them valence electrons.
Alkali metal- Atomic number
- 3
- Atomic mass
- 7 u
- Valence electrons
- 1
- Protons · neutrons
- 3 · 4
- Electrons per shell
- 2, 1
- At room temperature
- solid
Bohr model of lithium
The Bohr model draws lithium as a nucleus of 3 protons and 4 neutrons, with its 3 electrons on 2 circular shells: 2 in shell 1, 1 in shell 2. Press Build the atom to watch the shells fill from the inside out. The outer ring (the L 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 lithium
1s² 2s¹
Short form (noble gas notation): [He] 2s¹. The [He] stands for the electrons of helium, the noble gas before it.
How many valence electrons does lithium have?
Lithium has 1 valence electron.
Lithium 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 | 3 | equal to the atomic number |
|---|---|---|
| Electrons | 3 | equal to the protons in a neutral atom |
| Neutrons | 4 | mass number 7 − 3 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.
Lithium properties
| Symbol | Li |
|---|---|
| Category | Alkali metal |
| Group · period · block | 1 · 2 · s |
| Atomic mass | 7 u |
| State at 25 °C | solid |
| Melting point | 453.6 K (181 °C, 357 °F) |
| Boiling point | 1,615 K (1,340 °C, 2,450 °F) |
| Density | 0.534 g/cm³ |
| Electronegativity (Pauling) | 0.98 |
| Atomic radius | 182 pm |
| First ionization energy | 5.392 eV |
| Electron affinity | 0.618 eV |
| Oxidation states | +1 |
| Common ion charge | +1 |
| Discovered | 1817 by Johan August Arfwedson |
Where lithium sits on the periodic table
Group 1: Hydrogen, Sodium, Potassium, Rubidium, Cesium, Francium.
Questions about lithium
How many valence electrons does lithium have?
Lithium has 1 valence electron.
How many protons, neutrons and electrons does lithium have?
A neutral lithium atom has 3 protons and 3 electrons. Its most common form has about 4 neutrons (mass number 7 − 3 protons).
What is the electron configuration of lithium?
1s² 2s¹, written in short form as [He] 2s¹.
What does the Bohr model of lithium look like?
A nucleus of 3 protons and 4 neutrons, circled by 2 electron shells holding 2, 1 electrons.
What is the atomic number of lithium?
3. The atomic number is the number of protons in the nucleus, and it is what makes an atom lithium.