* Electronegativity: Nonmetals have a higher electronegativity than metals. This means they have a stronger attraction for electrons.

* Gaining Electrons: In order to become negatively charged (anions), atoms gain electrons. Nonmetals are more likely to gain electrons due to their higher electronegativity.

* Octet Rule: Nonmetals tend to gain electrons to achieve a stable octet configuration (8 electrons in their outermost shell).

Examples:

* Oxygen (O) - Forms the oxide ion (O^2-)

* Chlorine (Cl) - Forms the chloride ion (Cl^-)

* Nitrogen (N) - Forms the nitride ion (N^3-)

Exceptions:

While most negative ions are nonmetals, there are some exceptions where metals can form negative ions. This occurs in compounds where the metal is bonded to highly electronegative elements like oxygen.

Example:

* Manganese (Mn) - Can form the manganate ion (MnO₄^2-)

Overall, the majority of negative ions are formed by nonmetals due to their strong tendency to gain electrons.