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,

Answer

A

Explanation

The placing of elements are as

a) Ionisation enthalpy increased along a period (as we move from left to right in a period) with decrease in atomic size and decreases down the group with increase in atomic size. Hence, carbon has the highest first ionisation enthalpy.
b) Metallic character decreases across a period but increases on moving down the group. Hence, aluminium has the most mettalic character.