Why does the energy required to remove an electron change as it does?
Furthermore, why does it take energy to remove an electron?
Loss of an electron from an atom requires energy input. The energy needed to remove an electron from a neutral atom is the ionization energy of that atom. It is easier to remove electrons from atoms with a small ionization energy, so they will form cations more often in chemical reactions.
Moreover, is energy released when an electron is removed?
When electrons are removed from an atom, that process requires energy to pull the electron away from the nucleus. Addition of an electron releases energy from the process. This means that more energy is released in the formation of a halide ion than for the anions of any other elements.
Atomic radius decreases from left to right within a period. This is caused by the increase in the number of protons and electrons across a period. One proton has a greater effect than one electron; thus, electrons are pulled towards the nucleus, resulting in a smaller radius. This is caused by electron shielding.