Question

Which of the following best helps to explain why the electron affinity for Be is less favorable than the electron affinity for Li?

a) The electron added to Be experiences a greater effective nuclear charge than the electron added to Li experiences.
b) The electron added to Be is shielded by more core electrons than the electron added to Li is.
c) The electron added to Be goes into a higher energy orbital than the electron added to Li goes into.
d) The electron added to Be goes into a higher electron shell than the electron added to Li goes into.

Answer 1

The electron affinity for Be is less favorable than Li because of the greater effective nuclear charge in Be, less effective shielding in Be's principal shell, and higher energy orbital for Be.

Step-by-step explanation:

The electron affinity for Be is less favorable than the electron affinity for Li because the electron added to Be experiences a greater effective nuclear charge than the electron added to Li experiences. The electrons in the same principal shell are not very effective at shielding one another from the nuclear charge in Be, unlike in Li where the electrons in the filled 1s² shell effectively neutralize two of the three positive charges in the nucleus. Additionally, the electron added to Be goes into a higher energy orbital than the electron added to Li goes into, which also contributes to the less favorable electron affinity for Be.