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Question: Answered & Verified by Expert
A metal crystallizes with a face-centered cubic lattice. The edge of the unit cell is $408 \mathrm{pm}$. The diameter of the metal atom is
ChemistrySolid StateNEETNEET 2012 (Screening)
Options:
  • A $288 \mathrm{pm}$
  • B $408 \mathrm{pm}$
  • C $144 \mathrm{pm}$
  • D $204 \mathrm{pm}$
Solution:
1242 Upvotes Verified Answer
The correct answer is: $288 \mathrm{pm}$
For fcc lattice,
$\begin{aligned}
& 4 r=\sqrt{2} a \\
& r=\frac{\sqrt{2}}{4} a=\frac{a}{2 \sqrt{2}} \\
& =\frac{408}{2 \sqrt{2}} \\
& =144 \mathrm{pm} \\
& \text {diameter } d=2 r=2 \times 144 \mathrm{pm} \\
& =288 \mathrm{pm}
\end{aligned}$

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