Question Detail

Atomicity is the total number of atoms. Mg(OH)2 has 1 Mg atom, 2 O atoms, and 2 H atoms, totaling 1+2+2 = 5 atoms. CO2 has 3 atoms, C2H5OH has 2+5+1+1 = 9 atoms, and Fe2O3 has 5 atoms (2+3), making it also correct, but since the question asks for 'which could represent' and provides a single correct answer in a multiple-choice context, Mg(OH)2 is a valid example. Note: Fe2O3 also has an atomicity of 5, indicating multiple correct possibilities in a set, but based on standard MCQ design, Mg(OH)2 is a clear example.