Question

Why do elements with large electron affinities tend to form mono atomic anions?

Answer 1

lectron affinity (E.A.) is the energy change that occurs when an electron is added to a gaseous atom. Electron affinity can further be defined as the enthalpy change that results from the addition of an electron to a gaseous atom. It can be either positive or negative value. The greater the negative value, the more stable the anion is.

(Exothermic) The electron affinity is positive

X(g)+e−→X⁻+Energy

(Endothermic) The electron affinity is negative

   X(g)+e−+Energy→X⁻

It is more difficult to come up with trends that describe the electron affinity. Generally, the elements on the right side of the periodic table will have large negative electron affinity. The electron affinities will become less negative as you go from the top to the bottom of the periodic table. However, Nitrogen, Oxygen, and Fluorine do not follow this trend. The noble gas electron configuration will be close to zero because they will not easily gain electrons.