A compound is formed by two elements A and B. The element B forms cubic close packed structure and atoms of A occupy 1/3 of tetrahedral voids. If the formula of the compound is A_xB_y, then the value of x + y is in option

1. 2

2. 5

3. 4

4. 3

Doubtly Asked 30 Oct 2026 NEET UG 2023 neet Save WhatsApp Report

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Best answer

Answer: 2. 5

Key idea: In ccp, if B atoms number N, there are N octahedral and 2N tetrahedral voids.

Take 1 unit cell: B = 4 atoms; tetrahedral voids = 8. A fills 1/3: \(8 \times \frac13 = \frac83\).

A : B = \(\frac83 : 4 = 2 : 3\), so the formula is \(\mathrm{A_2B_3}\).

x + y = 2 + 3 = 5. Option 2.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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