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) Moving along a period, ionisation enthalpy increases and moving down a group ionisation enthalpy decreases. Therefore, C or Carbon has the highest first ionisation enthalpy.
(ii) The metallic character increases while moving down the group and decrease along a period, so, Al has the most metallic character.