Helium (He)
1s². 0 unpaired electrons, period 1, group 18, 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.
HeHelium, Z = 2, 4.003 u
1s2
In full: 1s²
- Blocks block
- Period1
- Group18
- Valence2
- Unpaired0
- MagneticDia
Last electron 1s
- n1shell
- l0s subshell
- m0orbital
- s−½spin down
Step by step
- Helium has 2 electrons.
- Fill in (n + l) order: 1s².
- Write the subshells in order of n: 1s².
- So: 1s².
Helium (He): the numbers
| Atomic number | 2 |
|---|---|
| Atomic mass | 4.003 u |
| Period | 1 |
| Group | 18 |
| Block | s block |
| Valence electrons | 2 |
| Unpaired electrons | 0 |
| Magnetic | diamagnetic |
| Last electron | 1s: n = 1, l = 0, m = 0, s = −1/2 |
Helium (He): quick answers
What is the electronic configuration of helium?
Helium has 2 electrons: 1s², or 1s² in short.
How many unpaired electrons does helium have?
Helium 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 helium?
The last electron goes into 1s: n = 1, l = 0, m = 0, s = −1/2. Orbitals fill from m = −l up, spin +½ first.