Beryllium (Be)
[He] 2s². 0 unpaired electrons, period 2, group 2, s block.
Element or ion
Type a symbol, a name or an atomic number, add a charge such as Fe3+ or Cl-, or tap an element in the table. Orbitals fill from m = −l up, spin +½ first.
BeBeryllium, Z = 4, 9.012 u
[He] 2s2
In full: 1s² 2s²
- Blocks block
- Period2
- Group2
- Valence2
- Unpaired0
- MagneticDia
Last electron 2s
- n2shell
- l0s subshell
- m0orbital
- s−½spin down
Step by step
- Beryllium has 4 electrons.
- Fill in (n + l) order: 1s² 2s².
- Write the subshells in order of n: 1s² 2s².
- Replace the helium core with [He]: [He] 2s².
Beryllium (Be): the numbers
| Atomic number | 4 |
|---|---|
| Atomic mass | 9.012 u |
| Period | 2 |
| Group | 2 |
| Block | s block |
| Valence electrons | 2 |
| Unpaired electrons | 0 |
| Magnetic | diamagnetic |
| Last electron | 2s: n = 2, l = 0, m = 0, s = −1/2 |
Beryllium (Be): quick answers
What is the electronic configuration of beryllium?
Beryllium has 4 electrons: 1s² 2s², or [He] 2s² in short.
How many unpaired electrons does beryllium have?
Beryllium has 0 unpaired electrons, so it is diamagnetic. Put one electron in each box of a subshell before pairing (Hund’s rule) to see them.
What are the quantum numbers of the last electron of beryllium?
The last electron goes into 2s: n = 2, l = 0, m = 0, s = −1/2. Orbitals fill from m = −l up, spin +½ first.