Complex sentence: Chemically, astatine behaves more or less as a halogen, being expected to form ionic astatides with alkali or alkaline metals; it is known to form covalent compounds with nonmetals, including other halogens.
Split into simpler sentences: Chemically, astatine behaves more or less as a halogen, being expected to form ionic astatides with alkali or alkaline metals. It is known to form covalent compounds with nonmetals, including other halogens.