Explanation:
The species with a positive charge over it, which means lack of electrons are called cations. Whereas the species with negative over it, meaning it has an excess of electrons with it are called anions.
From the list given the cations are
H+, Ba2+, Hg2+, Li+, Ca2+ and Fe2+
Whereas anions from the list are
O-2, Br-5, F-, S-2.
A Combination of cation and anions make an ionic compound in which cation is written first and then anion.
