Oxides BeO and CaO are crystals in which metal ions (Be++, Ca++) and oxygen ions (O--) are ionically bonded. At this time, oxygen ions are arranged in an FCC crystal structure, and metal ions are located in an octahedral void created in the FCC arrangement of oxygen ions. If the radius of the beryllium ion (Be++) is 0.31  and the radius of the calcium ion (Ca++) is 0.99 , among BeO and CaO oxides, which oxide has the most lattice transformation, and explain the reason.