Sodium metal crystallizes in a body centred cubic lattice with a unit cell edge of $4.29 \mathring{A}$. The radius of sodium atom is approximately :

Question

$\begin{array}{1 1} 1.86 \mathring{A} \\ 3.22 \mathring{A} \\ 5.72 \mathring{A} \\ 0.93 \mathring{A} \end{array}$