# What is the electron configuration of Cd2+?

Nov 12, 2015

$\left[\text{Kr}\right] 4 {d}^{10}$

#### Explanation:

Your starting point here will be the electron configuration of a neutral cadmium atom.

Cadmium, $\text{Cd}$, is located in period 5, group 12 of the periodic table and has an atomic number equal to $48$. This means that a neutral cadmium atom will have a total of $48$ electrons surrounding its nucleus.

This also tells you that the ${\text{Cd}}^{2 +}$ cation, which has two electrons less than the neutral atom, will have a total of $46$ electrons.

So, the electron configuration of a neutral cadmium atom looks like this

$\text{Cd: } 1 {s}^{2} 2 {s}^{2} 2 {p}^{6} 3 {s}^{2} 3 {p}^{6} 4 {s}^{2} 4 {p}^{6} 4 {d}^{10} 5 {s}^{2}$

Alternatively, you can use the noble gas shorthand notation to write cadmium's electron configuration based on that of krypton, the noble gas that comes before cadmium in the periodic table

"Cd: " ["Kr"] 4d^10 5s^2

Now, the ${\text{Cd}}^{2 +}$ cation is formed when cadmium loses the electrons that are highest in energy. As you can see in the electron configuration, the two electrons that occupy the 5s-orbital match this profile.

Therefore, the electron configuration of the ${\text{Cd}}^{2 +}$ cation will be

"Cd"^(2+): ["Kr"] 4d^10