An element with molar mass 2 .7 × 10 ^ - 2 kg mol ^ - 1 forms a...

Density = $\dfrac{Z \times M}{{N}_{a} \times Volume}$

$d = \dfrac{Z \times 27}{6 . 02 \times {10}^{23} \times {\left[4 . 05 \times {10}^{- 3}\right]}^{3}}$

$2 . 7 = \dfrac{Z \times 27}{6 . 02 \times {10}^{23} \times {\left[4 . 05 \times {10}^{- 3}\right]}^{3}}$

$Z =4 ⇒ fcc$ unit cell

For $fcc$

unit cell $4r = \sqrt{2}a$

$r = \dfrac{1 . 414 \times 405}{4}$

$= 143 . 1675pm$

$= 143 . 17pm$