Which of the following metals has an $hcp$ crystal structure?

Calculate the packing efficiency in a simple cubic metal crystal.

If the number of atoms in a unit cell is $2$,then the number of tetrahedral and octahedral voids will be ....... and ....... respectively.

In a metal oxide,$O^{2-}$ ions are arranged in $hcp$ lattice while metal ions occupy $2/3$ of the octahedral voids. The simplest formula of the oxide is:

If a compound (oxide) has an $hcp$ arrangement and the cations $M$ occupy two-thirds of the octahedral voids,the formula of the compound is:

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