Which of the following compounds does not contain a polyatomic ion? How do you determine this?

calcium carbonate
calcium sulfate
calcium phosphate
calcium sulfide?

1 Answer
Jun 3, 2018

Calcium Sulfide: "CaS"

Explanation:

A polyatomic ion is an ion with multiple atoms.

Polyatomic ions examples:

  • sulfate: "SO"_4^(2-)
  • phosphite: "PO"_3^(3-)
  • ammonium: "NH"_4^+

Monoatomic ions examples:

  • chloride: "Cl"^-
  • iron(III): "Fe"^(3+)
  • oxide: "O"^(2-)

Most monoatomic anions end with -ide, such as oxide and fluoride. Calcium ("Ca") sulfide ("S") would follow that rule.