Question

Which of these chemical formulas is incorrect, and why?

a) MgSO4, because the net charge is not zero.
b) AsRb, because the anion symbol should be second.
c) BeCl2, because the net charge is zero.
d) NaF, because a metal and nonmetal cannot form a binary ionic compound.

Answer 1

The incorrect chemical formula is b) AsRb because the correct notation for binary ionic compounds requires the metal (cation) to be written first, followed by the nonmetal (anion). All other options are correct, as MgSO4, BeCl2, and NaF are all neutrally charged compounds.

Step-by-step explanation:

The chemical formula that is incorrect is b) AsRb, because the anion symbol should be second. In binary ionic compounds, the metal (which forms the cation) is written first, followed by the nonmetal (which forms the anion). For AsRb, arsenic (As) is a metalloid, and rubidium (Rb) is a metal; this contradicts the proper formula notation where the cation should come first. Thus, the correct formula would have rubidium first, forming RbAs if they were to form a compound.

All other options are actually correct: a) MgSO₄ has a net charge of zero, since the Mg²⁺ cation balances the SO₄²⁻ anion. c) BeCl₂ is also correct because beryllium forms a Be²⁺ ion and chlorine forms a Cl- ion, resulting in a neutral compound with the formula BeCl₂. d) NaF is a binary ionic compound consisting of the sodium cation (Na⁺) and the fluoride anion (F⁻), and their combination is entirely possible and common.