Co²⁺ ion
[Ar] 3d⁷. 3 unpaired electrons, paramagnetic.
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.
Co2+Cobalt ion, 25 electrons
[Ar] 3d7
In full: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷. Co loses 4s²
Co loses 4s²
- Blockd block
- Period4
- Group9
- Outer shell15
- Unpaired3
- MagneticPara
Last electron 3d
- n3shell
- l2d subshell
- m−1orbital
- s−½spin down
Step by step
- Cobalt has 27 electrons: [Ar] 3d⁷ 4s².
- The ion has 2 fewer, 25 electrons. Remove them from the highest n first.
- Co loses 4s².
- Co²⁺ ion: [Ar] 3d⁷, in full 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷.
Co²⁺ ion: the numbers
| Atomic number | 27 |
|---|---|
| Electrons | 25 |
| Period | 4 |
| Group | 9 |
| Block | d block |
| Electrons in the outer shell | 15 |
| Unpaired electrons | 3 |
| Magnetic | paramagnetic |
| Last electron | 3d: n = 3, l = 2, m = −1, s = −1/2 |
Co²⁺ ion: quick answers
What is the electronic configuration of Co²⁺?
Co²⁺ has 25 electrons: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁷, or [Ar] 3d⁷. Co loses 4s².
How many unpaired electrons are there in Co²⁺?
Co²⁺ has 3 unpaired electrons, so it is paramagnetic.
Why does Co lose its outer electrons first?
Electrons leave from the highest n first. The 4s level fills before 3d, but once 3d holds electrons the 4s electrons are the outermost, so they are lost first.