73) A compound alloy of gold and copper crystallizes in a cube lattice in which the gold atoms occupy the lattice points at the corners of cube and copper atoms occupy the centers of each of the cube faces. The formula of this compound is:

74) The unit cell of a metallic element of atomic mass 10⁸ and density 10.5 gm⁄cm², is a cube with edge length of 409 pm. The structure of the crystal lattice is:

75) Copper metal has a fcc structure with a unit cell length of 0.361 nm. Picturing copper ions in contact along the face diagonal, the apparent radius of the copper ion is:

76) Which one of the following metal oxides is antiferromagnetic in nature?

77) A fcc unit cell of aluminium contains the equivalent of how many atoms?