Answer :
Here we have to get the electronic configuration of lithium element.
The electronic configuration of lithium (Li) is 1s²2s¹.
The lithium posses 3 electrons. The filling up the electrons in the orbitals depends upon the number of electrons can be accommodated in the particular orbital.
We know the filling of electrons is done from the low energy orbital to high energy orbital. The energy chrome of the s, p, d and f orbitals are s<p<d<f.
And The -s, -P, -d and -f orbital can accommodate 2, 6, 10 and 14 electrons respectively. As the number of electrons in lithium is 3. The 3 electrons can be present as 1s²2s¹.