Which factor increases the electron affinity of an atom?

The concept of electron affinity refers to the energy change that occurs when an atom gains an electron. A more negative electron gain enthalpy indicates that the process is more exothermic; that is, it releases more energy when an electron is added to the atom. This implies that the atom has a strong tendency to accept an additional electron, leading to an increase in its electron affinity.

When the electron gain enthalpy is more negative, it suggests that there is a favorable interaction between the incoming electron and the nucleus or the electron cloud of the atom, enhancing the stability of the ion formed after gaining the electron. This increased stability directly correlates with a higher electron affinity.

In contrast, a smaller atomic radius does not inherently increase the electron affinity; while it may allow for greater attraction between the nucleus and the added electron, it is not the primary factor influencing electron affinity. Similarly, considering the atomic number or the principal quantum number, these factors primarily relate to size and shielding rather than a direct increase in the tendency to gain electrons.