# What is the electron configuration of Li+?

Feb 1, 2016

${\text{Li}}^{+} : 1 {s}^{2}$

#### Explanation:

Your starting point here will be the electron configuration of a neutral lithium atom, $\text{Li}$.

A quick look in the periodic table will reveal that lithium is located in period 2, group 1, and that it has an atomic number equal to $3$.

This means that a neutral lithium atom will have a total of $3$ electrons surrounding its nucleus. Its electron configuration will be

$\text{Li: } 1 {s}^{2} \textcolor{red}{2} {s}^{1}$

Now, the lithium cation, ${\text{Li}}^{+}$, is formed when lithium loses the electron located on its outermost shell $\to$ its valence electron. This electron is located on the second energy level, in the 2s-orbital.

This means that the electron configuration of the ${\text{Li}}^{+}$ cation will be

${\text{Li}}^{+} : 1 {s}^{2}$

To write this using noble gas shorthand notation, use the electron configuration of the noble gas that comes before lithium in the periodic table.

Helium, $\text{He}$, has the electron configuration

$\text{He: } 1 {s}^{2}$

This means that you have

"Li"^(+): ["He"]

Here the notation $\left[\text{He}\right]$ is meant to represent the electron configuration of helium.