How do you determine the chemical formula of an ionic compound from the name of the compound?

Answer 1

From the name, first write down the metal with the charge, followed by the non metal with the charge. Consider the charge on each, and then apply subscripts as needed to make the overall charge zero.

Som examples:

Sodium chloride: Na⁺ is the metal, Cl^- is the non metal; NaCl is the formula (neutral)

Lead(IV) oxide: Pb⁴⁺ is the metal, O^2- is the non metal; PbO₂ is the formula (neutral)

Lithium sulfide: Li⁺ is the metal, S^2- is the non metal; Li₂S is the formula (neutral)

If you have polyatomic ions, you must learn/memorize them along with their associated charges.

Examples:

Ammonium chloride: NH₄⁺ is the polyatomic cation, Cl^- is the non metal anion; NH₄Cl is the formula

Ammonium sulfate: NH₄⁺ is the polyatomic cation, SO₄^2- is the polyatomic anion; (NH₄)₂SO₄ is the formula

Copper(II) phosphate: Cu²⁺ is the metal, PO₄^3- is the polyatomic anion; Cu₃(PO₄)₂ is the formula