Question

Sodium metal crystallises in a body centred cubic lattice with a unit cell edge of $4.29\stackrel{\circ }{A}$. The radius of $Na$ atom is approximately.

• A. $0.93\stackrel{\circ }{A}$
• B. $1.86\stackrel{\circ }{A}$
• C. $3.22\stackrel{\circ }{A}$
• D. $5.72\stackrel{\circ }{A}$

Answer 1

The correct option is B $1.86\stackrel{\circ }{A}$

$a\sqrt{3}=4r$
$r=\frac{4.29\times 1.732}{4}=1.857=1.86\stackrel{\circ }{A}$.