What is the electron configuration of Li+?

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

Your starting point here will be the of a neutral lithium atom, ##"Li"##.

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

This means that a neutral lithium atom will have a total of ##3## electrons surrounding its nucleus.

Its 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 . 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 , use the electron configuration of the noble gas that comes before lithium in .

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.