Among the elements B, Al, C and Si,
(i) which element has the highest first ionisation enthalpy?
(ii) which element has the most metallic character? Justify your answer in each case.
(i) Carbon has the highest ionisation enthalpy. It increases from left to right across the period and decreases as we go down the group.
(ii) Aluminium has the most metallic character. As we move down, the metallic character increases and decreases across the period from left to right.