Oxygen (O)
[He] 2s² 2p⁴. 2 unpaired electrons, period 2, group 16, p 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.
OOxygen, Z = 8, 15.999 u
[He] 2s2 2p4
In full: 1s² 2s² 2p⁴
- Blockp block
- Period2
- Group16
- Valence6
- Unpaired2
- MagneticPara
Last electron 2p
- n2shell
- l1p subshell
- m−1orbital
- s−½spin down
Step by step
- Oxygen has 8 electrons.
- Fill in (n + l) order: 1s² 2s² 2p⁴.
- Write the subshells in order of n: 1s² 2s² 2p⁴.
- Replace the helium core with [He]: [He] 2s² 2p⁴.
Oxygen (O): the numbers
| Atomic number | 8 |
|---|---|
| Atomic mass | 15.999 u |
| Period | 2 |
| Group | 16 |
| Block | p block |
| Valence electrons | 6 |
| Unpaired electrons | 2 |
| Magnetic | paramagnetic |
| Last electron | 2p: n = 2, l = 1, m = −1, s = −1/2 |
Oxygen (O): quick answers
What is the electronic configuration of oxygen?
Oxygen has 8 electrons: 1s² 2s² 2p⁴, or [He] 2s² 2p⁴ in short.
How many unpaired electrons does oxygen have?
Oxygen has 2 unpaired electrons, so it is paramagnetic. 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 oxygen?
The last electron goes into 2p: n = 2, l = 1, m = −1, s = −1/2. Orbitals fill from m = −l up, spin +½ first.