Question

Of the following atoms, which has the largest first ionization energy?

A). P

B). N

C). C

D). Si

E). B

Answer 1

B, C and N lies in period 2 of periodic table

Si and P lies in period 3 of periodic table

C and Si are in same group

N and P are in same group

Rule 1:

Ionisation energy increases we move from left to right in a period.

So,

B < C < N and

Si < P

Rule 2:

Ionisation energy decreases we move down a group.

So,

Si < C

P < N

If we analyse relations formed after Rule 1 and Rule 2, we can say that:

N has largest first ionisation energY

Answer: B