Question

What is the electron configuration of Li+?

Answer 1

`"Li""^(+): 1s^2`

Explanation:

Your starting point here will be the electron configuration of a neutral lithium atom, `"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

`"Li: " 1s^2 color(red)(2)s^1`

Now, the lithium cation, `"Li"^(+)`, is formed when lithium loses the electron located on its outermost shell `->` its valence electron. This electron is located on the second energy level, in the 2s-orbital.

This means that the electron configuration of the `"Li"^(+)` cation will be

`"Li"^(+): 1s^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, `"He"`, has the electron configuration

`"He: " 1s^2`

This means that you have

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

Here the notation `["He"]` is meant to represent the electron configuration of helium.