Which of the following lattices has the highest packing efficiency: $(i)$ simple cubic,$(ii)$ body-centred cubic,and $(iii)$ hexagonal close-packed lattice?

Give two examples of metals that crystallize in the $hcp$ (hexagonal close-packed) structure.

$A$ compound is formed by two elements $M$ and $N$. Element $N$ forms a hexagonal closed pack $(HCP)$ array with $2/3$ of the octahedral holes occupied by $M$. The formula of the compound is $....$

What is the percentage of void space in $hcp$ and $ccp$ structures (in $\%$)?

How many unit cells share a corner of a unit cell in a crystal lattice?

In a face-centred cubic arrangement of $A$ and $B$ atoms,$A$ atoms are at the corners of the unit cell and $B$ atoms are at the face centres. If three of the $B$ atoms are missing from the face centres in the unit cell,what is the simplest formula of the compound?