The number of octahedral voids per lattice site in a lattice is _________. (Rounded off to the nearest integer)

The unit cell of copper corresponds to a face centered cube of edge length 3.596 $$\mathop A\limits^o $$ with one copper atom at each lattice point. The calculated density of copper in kg/m³ is ___________. [Molar mass of Cu : 63.54 g; Avogadro Number = 6.022 $$\times$$ 10²³]

The coordination number of an atom in a body-centered cubic structure is _______.
[Assume that the lattice is made up of atoms.]

An element with molar mass 2.7 $$ \times $$ 10^-2 kg mol^-1 forms a cubic unit cell with edge length 405 pm. If its density is 2.7 $$ \times $$ 10³ kg m^-3, the radius of the element is approximately ______ $$ \times $$ 10^-12 m (to the nearest integer).