Duplicate
write a chemical equation representing the second ionization energy for lithium.

Ionization energy is the tendency of an atom to release an electron.
It decreases down the group and increases across the period in the periodic table:
First ionization energy means removal of electron form Li:
Li --> Li+ + 1 e- 
The 2nd ionization energy is removing a 2nd electron from that resulting cation: 
Li+ --> Li2+ + 1e- 

Carbon based or cells?