Full configuration
1s² 2s²
In the short form, [He] stands for the 2 electrons of helium, the noble gas before beryllium. 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
Beryllium is in group 2, period 2, in the s-block. It has 0 unpaired electrons in the ground state, so the atom is diamagnetic.
Configuration of beryllium ions
| Ion | Configuration | Unpaired | Moment (BM) |
|---|---|---|---|
| Be²⁺ | 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
| Z | Element | Configuration |
|---|---|---|
| 1 | Hydrogen | 1s¹ |
| 2 | Helium | 1s² |
| 3 | Lithium | [He] 2s¹ |
| 5 | Boron | [He] 2s² 2p¹ |
| 6 | Carbon | [He] 2s² 2p² |
| 7 | Nitrogen | [He] 2s² 2p³ |
Questions students ask
What is the electronic configuration of beryllium?
[He] 2s², or in full, 1s² 2s². Beryllium has atomic number 4.
How many electrons are in each shell of beryllium?
2, 2 (K, L, M, N… shells in order).
How many unpaired electrons does beryllium have?
0 in the ground state, so beryllium atoms are diamagnetic.
What is the electronic configuration of Be²⁺?
1s², with 0 unpaired electrons.