Question

Rank the elements Be, B, C, N, and O inside of increasing first ionization energy. Explain your reasoning.

Short answer

The correct order of increasing the first ionization energy is:

B<Be<C<O<N.

Step-by-step solution

Describe the general trend of ionization energy in the periodic table

Ionization generally increases in a period and decreases down the group.

Write the electronic configuration of the given elements

Be(4)=1s²2s² (completely filled 2s orbital)

B(5)=1s²2s²2p¹

C(6)=1s²2s²2p²

N(7)=1s²2s²2p³

O(8)=1s²2s²2p⁴

Apply the concept of extra stability of half and completely filled orbitals.

We can see that Be has completely filled 2s orbitals, so it will havehigherionization energy than B. The next ionization energy will be of C as ionization energy increases over a period.

N has a half-filled 2p orbital, so it is more stable & hence will have higher ionization energy than O.

B<Be<C<O<N