Three elements X, Y and Z are in the 3ʳᵈ period of the periodic table. The oxides of X, Y and Z, respectively, are basic, amphoteric and acidic. The correct order of the atomic numbers of X, Y and Z is :

Solution

Chemistry ma’am · 3 steps

Across period 3, oxides go from basic to amphoteric to acidic, so the order of oxide nature is the order of Z.

1. Trend across period. Moving left to right in period 3, atomic number rises and metallic character falls. Metal oxides are basic, non-metal oxides are acidic, and the ones in between are amphoteric.

   Element	Atomic number	Oxide	Nature
   Na	11	Na₂O	basic
   Mg	12	MgO	basic
   Al	13	Al₂O₃	amphoteric
   Si	14	SiO₂	weakly acidic
   P, S, Cl	15, 16, 17	P₄O₁₀, SO₃, Cl₂O₇	acidic, getting stronger

2. Place X, Y, Z. X has a basic oxide, so it is Na or Mg, before Al. Y has an amphoteric oxide, so Y is Al. Z has an acidic oxide, so it lies after Al, among Si to Cl.
3. So. The atomic numbers increase as X < Y < Z, which is option (d).

The idea to keep. In any period, oxides turn from basic to amphoteric to acidic as you go left to right. Read the oxide's nature and you know where the element sits.

Answer from the NTA final answer key. Solution by PrepWiser.