Chalcogenides

Molecular compounds comprise H₂S and its analogs, and several organic compounds. The hydrides are made through the action of Brønsted acids on metal chalcogenides. They are very toxic gases, weakly acidic in water (example for H₂S, pK₁=6. 8, pK₂=14.2). Several polysulfanes H₂Sn consisting of S-S bonds are also well known.

Solid chalcogenides are formed through all metallic elements and through several nonmetals. Only with the generally electropositive metals do they generally have similar structures like oxides. Compounds MX (which are often of variable stoichiometry) comprise the nickel arsenide or identical structures where metal-metal bonding is exist, with transition metals. MX₂ compounds either comprise layer structures (example TiS₂, TiSe₂, TiTe₂, all CdI₂ types) or structures consisting of diatomic ions (example FeS₂ has S₂ ^2- units and so properly is a compound of Fe^II not Fe^IV).

Electropositive metals' Chalcogenides are decomposed through water giving hydrides like H₂S, but those of less electropositive elements (frequently the ones forming sulfide ores) are insoluble in water.