In sodium chloride crystal, the unit cell edge length is . The option(s) representing correct combin — Solid State Chemistry Question

💡 Solution & Explanation

Taking an Na$^+$ ion at the origin: its 1st nearest neighbours are 6 Cl$^-$ at $a/2$; 2nd nearest are 12 Na$^+$ at $a/\sqrt{2} \approx 0.707a$; 3rd nearest are 8 Cl$^-$ at $\sqrt{3}a/2 \approx 0.866a$; 4th nearest are 6 Na$^+$ at $a$; and 5th nearest are 24 Cl$^-$ at $\sqrt{5}a/2 \approx 1.118a \approx 1.12a$. All options represent the correct combinations. Therefore, correct answer is A,B,C,D.