Question

Which has larger second ionization energy, lithium or beryllium? Why?

Short answer

Lithium (Li) has larger second ionization energy.

Step-by-step solution

Identifying whether lithium has higher second ionization energy or not  

The number ofextra valence electronsinlithium is 1 and the number of extra valence electrons inberyllium is 2

Removing 2 electrons from beryllium creates Be²⁺and removing 1 electron from Lithium creates Li+.

Hence, Lithium has higher second ionization energy.

Identifying why beryllium has lower second ionization energy as compared to lithium  

In beryllium, the number of extra valence electrons is 2. So, both the electrons can be ionized easily.

In the case of Lithium, the number of extra valence electrons is 1, and hence, in the second ionization, the electron will be held tighter by the nucleus. This means that the electron to be ionized will require higher second ionization energy.