Explain why the first ionisation of magnesium is 736 kJ mol-1whilst that of beryllium is 900 kJ mol-1.
Mg has an electronic configuration of 1s22s22s63s2, Be has an electronic configuration of 1s22s2.
Magnesium has a shell more than Be.
The electrons of Magnesium are further away than those of Be.
The Ionisation Energy decreases for Mg.