Both NaCl and KCl crystallize with the fcc structure. However, the X-ray powder diffraction pattern of NaCl corresponds to the fcc structure whereas, that of KC corresponds to simple cubic structure. This is because
(a)$\mathrm{K}^{+}$ and $\mathrm{Cl}^{-}$ are isoelctronic
(b)$\mathrm{Na}^{+}$ and $\mathrm{Cl}^{-}$ are isoelctronic
(c)$\mathrm{K}^{+}$ and $\mathrm{Cl}^{-}$ are disordered in the lattice crystal
(d)KCl has anti-site defects
Answer
Answer: A ✓ checked by 4AB · confidence high
Explanation
K⁺ and Cl⁻ are isoelectronic (18 e) and scatter X-rays almost identically, so the two sublattices look alike and the pattern indexes as a simple cubic cell of half the edge; Na⁺ (10 e) and Cl⁻ (18 e) scatter differently.