If lattice parameter for a crystalline structure is 3.6 Å, then atomic radius in fcc crystal in Å is –

7.20 Å 1.80 Å 1.27 Å 2.90 Å

1.27 Å

Atomic radius for fcc crystal is $r=\frac{a}{2\sqrt{2}}=\frac{3.6}{2\sqrt{2}}Å=1.27Å$