Question

What is electron affinity and how it depends on atomic size, effective nuclear charge and screening factor?

Answer 1

Hint: It is found that energy change occurs when an atom gains an electron, and also energy is released which is called electron affinity. Its value is mainly used to determine whether an atom will act as electron donor or electron acceptor.

Complete answer:
- We can say that electron affinity is the amount of energy release to add an electron. There are several factors that can affect electron affinity like atomic size, effective nuclear charge and screening factor.
- We will first discuss about how electron affinity depends on atomic size:
It is found that the smaller the size of an atom is, the closer the outermost shell is. And therefore, there is a stronger force of attraction found in between the electron and the nucleus. Which means that for smaller atoms the electron affinity is higher. In the periodic table we can see that atomic radius increases from top to bottom and therefore electron affinity increases from bottom to top.
- Now we will discuss about how electron affinity depends on screening factor:
It is found that as the screening factor increases across down the group, there is decrease in electron affinity as the incoming electron doesn’t have much attraction with the nucleus. We can say that screening factor is inversely proportional to electron affinity.
- Now we will discuss how electron affinity depends on nuclear charge: As we know that nuclear charge is also called an atomic number, that is the same as the number of protons. It is found that if there are more protons than there will be more attraction to the electrons. Basically, in the periodic table, from left to right nuclear charge increases due to which there is a great attraction to the incoming electrons. Hence, we can say that the electron affinity also increases from left to right across a period.

Note: - We must remember that electron affinity is the energy released which means that the reaction is exothermic. And we know that if the reaction is exothermic, the change in energy is negative, that is the electron affinity is positive.
- Higher electron affinity indicates that an atom accepts electrons more easily. Whereas, a lower electron affinity indicates that an atom doesn’t accept electrons easily.