Ionic Bonding - Opposite charges attract each other in solid state. These crystalline structures are hard and brittle until dissolved into solution. Electrons are completely transferred between atoms.

Covalent Bonding - These molecules are usually found as solid, liquid or gas at room temperature. These compounds have atoms that share electrons and both atoms simultaneously can fulfill their outermost orbital (octet rule) and become stable.

Metallic Bonding - This type of bonding results in solid compounds (except for Hg) at room temperatures. These compounds are mostly lustrous, and all are quite conductive. This is due to a sea of de-localized electrons stabilizing positively charged ions.