Identify the cations (electropositive ions) and anions (electronegative ions) in the following compounds:

(a) CH₃COONa

(b) NH₄Cl

(c) PbCl₂

(d) MgO

Give an example of a divalent anion and a trivalent cation. Write the formula of the compound formed by their combination.

State the number of atoms present in each of the following:

(a) PO₄^3-

(b) P₂O₅

(c) H₂SO₄

(d) SO₄^-2

Depending on the number of oxygen atoms in the anions, the names of some acids and their formulae are given. Write the formula of their corresponding salts.