GEOLOGY

Detailed explanation-1: -A unit cell is the smallest representation of an entire crystal. The hexagonal closest packed (HCP) has a coordination number of 12 and contains 6 atoms per unit cell. The face-centered cubic (FCC) has a coordination number of 12 and contains 4 atoms per unit cell.

Detailed explanation-2: -The simple cubic unit cell is delineated by eight atoms, which mark the actual cube. These are corner atoms, so each one only contributes one eighth of an atom to the unit cell, thus giving us only one net atom.

Detailed explanation-3: -A FCC unit cell contains four atoms: one-eighth of an atom at each of the eight corners (8×18=1 atom from the corners) and one-half of an atom on each of the six faces (6×12=3 atoms from the faces).

Detailed explanation-4: -a unit cell consists of a cube in which there are A atoms at the corners and B atoms at the face centres and A atoms are missing from 2 corners in each unit cell. What is the simplest formula of the compound?

Detailed explanation-5: -An atom on a face is shared by two unit cells, so only half of the atom belongs to each of these cells. An atom on an edge is shared by four unit cells, and an atom on a corner is shared by eight unit cells.