There are a number of compounds that could be called iron sulfide.
Iron(II) sulfide FeS. This is pyrophoric
Iron(III) sulfide Fe2S3 . This is rapidly oxidised by air.
Iron(II,III) sulfide Fe3S4, which is found in nature as a mineral greigite and is ferromagnetic like Fe3O4
The chemical formula of caesium sulphide is Cs2S.
1 : 1
Formula: CaS
The chemical formula of silver sulfide is Ag2S.
S-1
NiS
S2-
The formula is: Li2S the "2" is a subscript
The chemical formula for sulphide is S^2-. It is composed of one sulfur atom bonded to two electrons, giving it a -2 charge.
The chemical formula for iron(II) dihydrogen phosphate is Fe(H2PO4)2.
The chemical formula for copper(I) sulfide is Cu2S.
The chemical formula for lead (IV) sulfide is written as PbS2.