The coordination number of a metal crystallising in a hexagonal close-packed $(HCP)$ structure is

In the $NaCl$ crystal structure,how many chloride ions surround each sodium ion?

Which of the following has a $4:2$ coordination number structure?

If three elements $A, B, C$ crystallize in a cubic solid lattice with $B$ atoms at the cubic centers, $C$ atoms at the center of edges, and $A$ atoms at the corners, then the formula of the compound is

The packing efficiency and coordination number of face-centred cubic $(FCC)$ lattice is

In the fluorite structure,the coordination number of the $Ca^{2+}$ ion is.....