Stoichiometry of oxide formation with O₂ Steps:

• Write balanced equations: Na (4Na + O₂ → 2Na₂O), Mg (2Mg + O₂ → 2MgO), Al (4Al + 3O₂ → 2Al₂O₃), P (P₄ + 5O₂ → P₄O₁₀).
• Find O₂ coefficient divided by element atoms coefficient for mole ratio.
• Compute per 1 mol atoms: Na (1/4 = 0.25), Mg (1/2 = 0.5), Al (3/4 = 0.75), P (5/4 = 1.25).
• Select lowest ratio (0.25 for Na).

Why D is correct:

• Sodium's +1 oxidation state in Na₂O yields 0.25 mol O₂ per mol Na atoms, lowest per balanced equation.

Why the others are wrong:

• A. Aluminum's +3 state in Al₂O₃ requires 0.75 mol O₂ per mol Al.
• B. Magnesium's +2 state in MgO requires 0.5 mol O₂ per mol Mg.
• C. Phosphorus's +5 state in P₄O₁₀ requires 1.25 mol O₂ per mol P.

Final answer: D