Among the elements, B, Al, C and Si,
a) which element has the highest first ionisation enthalpy?
b) which element has the most metallic character? Justify your answer in each case,

Explanation

Arranging the elements into different groups and periods :

(i) Ionization enthalpy increases along a period and
decreases down a group. Therefore, C has the highest first ionization enthalpy.
(ii) Metallic character decreases along a period and increases down a group. Therefore, Al has the most metallic character.