Question

Copper metal crystallizes in $FCC$ lattice. Edge length of unit cell is $362pm$. The radius of largest atom that can fit into the voids of copper lattice without disturbing it is

• A. $53pm$
• B. $45pm$
• C. $93pm$
• D. $87pm$

Answer 1

The correct option is A $53pm$

The edge length $a$ is $362$ pm.

For fcc structure, the radius of $Cu$ metal $R=\frac{a}{2\sqrt{2}}=0.3535a=0.3535\times 362pm=127.9pm$

For an octahedral void, the radius ratio is in a range of $0.414to0.732$.

For largest atom to be fit into the octahedral void, $r=0.732R=0.732\times 127.9pm=53pm$

Thus, the radius of the largest atom that can fit into the voids of copper lattice without disturbing it is $93pm$.

Option A is correct.