If Na2SO4 were to dissolve in water, how many ions per molecule would be formed?

Three (3) = > 2Na⁺ and 1SO₄²⁻

Explanation:

Na₂SO₄ = > 2Na⁺ + SO₄²⁻

Note: one can easily determine the cation-anion separation during aqueous ionization if one reads the formula left to right = > place an imaginary line after the 1st metal of the molecular formula = > left of line is cation and right of line anion.

Na₂SO₄ = > Na₂ | SO₄ = > 2Na⁺ + SO₄²⁻ (3 ions)

CaCO₃ = > Ca | CO₃ = > Ca₂⁺ + CO₃²⁻ (2 ions)

Ni (NO₃) ₂ = > Ni | (NO₃) ₂ = > Ni²⁺ + 2NO₃⁻ (3 ions)

Ca₃ (PO₄) ₂ = > Ca₃ | (PO₄) ₂ = > 3Ca²⁺ + 2PO₄³⁻ (5 ions)