The radius of an atom of this element $d=\large\frac{xM}{a^3N_A}$
Where
$d$=Density of the element
$z$=no. of atoms
$a=1.469\times 10^{-10}$ atom= $146.9\times 10^{-10}cm$
$N_A=6.023\times 10^{23}$
$M = \large\frac{da^3N_A}{z}$
$\;\;\;\;=\large\frac{19.3\times 146.9\times 10^{-10}\times 6.023 \times 10^{23}}{2}$
$\;\;\;\;=183.5g$
$r=\large\frac{\sqrt 3}{4}$$a$
$\;\;=\large\frac{\sqrt 3\times 1.469\times 10^{-8}}{4}$
$r=0.634\times 10^{-8}$cm