# Why is the electron configuration for Ni 1s^2 2s^2 2p^4 3s^4 3p^4 4s^2 3d^8 and not 1s^2 2s^2 2p^4 3s^4 3p^4 3d^10?

Aug 22, 2016

Neither electron configuration for Nickel is correct.

#### Explanation:

An s sublevel can only hold two electrons because it has only one orbital. Each orbital in any sublevel can hold only two electrons. Both of the electron configurations in your question have a $\text{3s"^4}$ sublevel, which is impossible.

The atomic number for nickel is 28. If it is neutral, one atom of nickel has 28 protons and 28 electrons. Both of the electron configurations for nickel in your question have only 26 electrons.

In the second configuration, the $\text{4s"^2}$ sublevel is missing.

Nickel's electron configuration is $\text{1s"^2"2s"^2"2p"^6"3s"^2"3p"^6"4s"^2"3d"^8}$. The $4 \text{s}$ sublevel fills before the $\text{3d}$ sublevel because the $\text{4s}$ sublevel has lower energy than the $\text{3d}$ sublevel.