Full configuration
1s² 2s¹
In the short form, [He] stands for the 2 electrons of helium, the noble gas before lithium. Only the electrons after it are written out.
Orbital diagram
1s↑↓
2s↑
Outer subshells only. Each box is an orbital; electrons fill singly first (Hund's rule), then pair up with opposite spins.
What the configuration tells you
Lithium is in group 1, period 2, in the s-block. It has 1 unpaired electron in the ground state, so the atom is paramagnetic.
Configuration of lithium ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| Li⁺ | 1s² | 0 | 0.00 |
Moment is the spin-only magnetic moment μ = √(n(n + 2)) Bohr magnetons, where n is the number of unpaired electrons.
Nearby elements
Questions students ask
What is the electronic configuration of lithium?
[He] 2s¹, or in full, 1s² 2s¹. Lithium has atomic number 3.
How many electrons are in each shell of lithium?
2, 1 (K, L, M, N… shells in order).
How many unpaired electrons does lithium have?
1 in the ground state, so lithium atoms are paramagnetic.
What is the electronic configuration of Li⁺?
1s², with 0 unpaired electrons.