Lithium (Li): electron configuration, atomic mass and facts
Lithium (Li) is element 3 of the periodic table, an alkali metal in period 2, group 1. Its electron configuration is [He] 2s1, with electrons arranged in shells 2, 1, and its standard atomic weight is 6.94 u.
💡 The lightest metal. It powers phone and electric-car batteries.
▶ Watch Lithium’s electrons orbit in the interactive periodic tableLithium at a glance
| Symbol | Li |
|---|---|
| Atomic number | 3 |
| Atomic mass | 6.94 u |
| Category | Alkali metal |
| Group | 1 |
| Period | 2 |
| Block | s-block |
| Electron configuration | 1s2 2s1 |
| Noble-gas shorthand | [He] 2s1 |
| Electrons per shell | 2, 1 |
| Outer-shell electrons | 1 |
| Electronegativity (Pauling) | 0.98 |
| State at 20 °C | solid |
| Flame test colour | crimson red |
Where is Lithium on the periodic table?
Lithium is in period 2, group 1, in the s-block. The period number matches its 2 electron shells, and the block names the subshell its last electrons fill. In the same group, Hydrogen sits directly above it and Sodium 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 Lithium
Put 3 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s¹ (3). In shorthand, [He] stands for the 2 electrons of helium, giving [He] 2s¹.
How electronegative is Lithium?
Lithium has a Pauling electronegativity of 0.98, ranking 92 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.
Lithium in the virtual lab
Faradium’s chemistry workbench includes these chemicals that contain lithium: Lithium chloride. Open the Chemistry Lab to experiment with them.
Frequently asked questions
What is the electron configuration of Lithium?
The electron configuration of Lithium (Li) is 1s2 2s1. In noble-gas shorthand it is written [He] 2s1.
How many electrons does Lithium have in each shell?
Lithium has 3 electrons arranged in shells as 2, 1. It has 1 electron in its outer shell.
What is the atomic mass of Lithium?
The standard atomic weight of Lithium is 6.94 u, so one mole of Lithium atoms has a mass of about 6.94 g.
Is Lithium a metal?
Yes. Lithium is an alkali metal.
Explore nearby elements
More alkali metals: Sodium, Potassium, Rubidium, Caesium, Francium. See all elements on the periodic table.