Non-cationic chemistry

Even though cationic chemistry has been highlighted above, other types of bonding are probable with the elements of all groups in this Section. These comprise the following.

• Covalent compounds. Compounds with predominantly covalent character comprise organometallic compounds.
• Anionic compounds. Under not usual circumstances, group 1 elements can form anions like Na^-. Some posttransition elements create polyatomic ions.
• Metal-metal bonding. This is particularly a characteristic of post-transition groups and can accompany several 'unusual' oxidation states, where Hg¹ (in fact Hg²⁺₂) is the most common instance.