Iron (II) oxide has a cubic structure and each unit cell has side 5 Å . If the density of the oxide is 4 g ` cm^(-3)` Calculate the number of ` Fe^(2+) and O^(2+)` ions presnent in each unit cell ( Molar mass of FeO = 72 ` " g mol"^(-1)`
`N_(A) = 6.02 xx 10^(23) "mol"^(-1)` )