How we can add electron to atom if it is too small?

When the electron affinity is positive, meaning energy is required to add an electron to the atom, why does kinetic energy have to be given to the added electron so it can bond to the atom?

• Answer:

  Ionisation energies are always concerned with the formation of positive ions. Electron affinities are the negative ion equivalent, and their use is almost always confined to elements in groups 6 and 7 of the Periodic Table. The first electron affinity is the energy released when 1 mole of gaseous atoms each acquire an electron to form 1 mole of gaseous 1- ions. It is the energy released (per mole of X) when this change happens. First electron affinities have negative values. For example, the first electron affinity of chlorine is -349 kJ mol-1. By convention, the negative sign shows a release of energy, not  as you state in your question.