Question

How is the ability to lose or accept electrons in the valence shell determined?

Answer 1

The ability to lose electrons is measured by the ionization energy. Higher the ionization energy, harder it will be for electrons to liberate from the atom, i.e., it will be hard to lose electrons. The ability to accept electrons is determined by the electron affinity. The higher the value of electron affinity, the higher will be the tendency to accept electrons.