In a crystal,Frenkel defect is observed only when the radius ratio is......

Which defect causes a decrease in the density of a crystal?

When electrons are trapped into the crystal in anion vacancy,the defect is known as

Missing of one monovalent cation and one monovalent anion from the crystal lattice is called

Which of the following molecular formula and type of defect are correct for the following statement?
"In $FeO$ crystal,some $Fe^{2+}$ ions are missing and the loss of positive charge is made up by the presence of $Fe^{3+}$ ions".

Analysis shows that nickel oxide has the formula $Ni_{0.98}O_{1.00}$. What fractions of nickel exist as $Ni^{2+}$ and $Ni^{3+}$ ions?