Question

Sodium metal crystallizes in a body centred cubic lattice with a unit cell edge of $4.29\AA$. The radius of sodium atom is approximately.
(AIEEE 2015)

• A. $1.86\AA$
• B. $0.93\AA$
• C. $5.72\AA$
• D. $3.22\AA$

Answer 1

The correct option is A $1.86\AA$

For body center unit cell,
$4r=a\sqrt{3}$
So, radius of sodium atom$=\frac{\sqrt{3}}{4}\times 4.29=1.857\approx 1.86\AA$