Among the elements B, Al, C and Si,

1. which element has the highest first ionisation enthalpy?

2.  which element has the most metallic character?

Justify your answer in each case.


The placing of elements are as

Period

Group-13

Group-14

2nd Period

Boron

Carbon

3rd Period

Aluminum

Silicon

(a) Ionisation enthalpy increases 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, aluminum has the most metallic character.