Element Atomic weight Atomic radius Common ion Ionic radius Be 9 amu 0.114 nm Be2 0.034 nm Mg 24.31 amu 0.160 nm Mg2 0.078 nm Pg 207.2 amu 0.175 nm Pb2 0.120 nm Si 28 amu 0.118 nm Si4 0.040 nm O 16 amu 0.060 nm O2- 0.132 nm Which Oxide will have a structore with a cation coordination number of 8