<u>Answer:</u> The density of metal X is 
<u>Explanation:</u>
We are given:
Atomic radius of metal X = 
To calculate the edge length, we use the relation between the radius and edge length for FCC lattice:

Putting values in above equation, we get:

To calculate the density of metal, we use the equation:

where,
= density
Z = number of atom in unit cell = 4 (FCC)
M = atomic mass of metal = 42.3 g/mol
= Avogadro's number = 
a = edge length of unit cell =
(Conversion factor:
)
Putting values in above equation, we get:

Hence, the density of metal X is 