Cations and anions
When a neutral atom loses one or more electrons, the total number of electrons decreases while the number of protons in the nucleus remains the same. The result is that the atom becomes a Cation—an ion with a net positive charge.
The opposite process can also occur. When a neutral atom gains one or more electrons, the number of electrons increases while the number of protons in the nucleus remains the same. The result is that the atom becomes an anion—an ion with a net negative charge.
Elements that form cations and anions
For groups 1, 2, 13, and 14, the elements have one to four valence electrons as neutral atoms, and they will usually give away these valence electrons to become ions—carbon
For groups 15 through 17, the charge is usually negative because these elements are more likely to gain than lose electrons.
Polyvalent cation are cations that can transfer 4-3 electrons to elements
Formulas and naming of basic ionic compounds
Always name the cation before the anion; in the chemical formula, the cation will always appear first as well.
When naming the cation within an ionic compound, we don't include the word ion or the charge unless it is a polyvalent cation.
Any ionic compound will have a net charge of zero. Another way of saying this is that cations and anions must always combine in such a way so that their charges cancel.
The number of cations and anions in the formula should be written as the lowest possible integer value. For example, the formula for sodium chloride is NaCI , not Na3CI3 or some other multiple of NaCI , even though the charges would still add up to zero.
Conclusion
Cations are positively charged ions formed when neutral atoms lose electrons; anions are negatively charged ions formed when neutral atoms gain electrons. It is possible to predict the charges of common monatomic ions by looking at the group numbers on the periodic table.
Many of the transition metals are polyvalent, which means they can form cations of multiple charges. When naming these cations or compounds containing these cations, it is necessary to specify their charge.