Question

The ionization enthalpy decreases as we go from top to bottom in the group, while it increases as we move from left to right in the period?

Answer 1

Hint : Periodic trends are specific patterns that are present in the periodic table that illustrate different aspects of a certain element, including its size and its electronic properties. Major periodic trends include: electronegativity, ionization energy, electron affinity, atomic radius, melting point and metallic character.

Complete Step By Step Answer:
Ionization energy is the energy required to remove an electron from a neutral atom in its gaseous phase. Ionization energy is the opposite of electronegativity. The lower this energy is, the more readily the atom becomes a cation.
Generally, elements on the right side of the periodic table have a higher ionization energy because their valence shell is nearly filled. Elements on the left side of the periodic table have low ionization energy because of their willingness to lose electrons and become cations. Thus, ionization energy increases from left to right on the periodic table.
Thus, the ionization energy of the elements within a period generally increases from left to right. This is due to valence shell stability. The ionization energy of the elements within a group generally decreases from top to bottom. This is due to electron shielding. The noble gas possesses very high ionization energies because of their full valence shells.

Note :
Electron shielding describes the ability of an atom’s inner electrons to shield its positively charged nucleus from its valence electrons. When moving to the right of a period, the number of electrons increases and the strength of shielding increases. As a result, it is easier for valence shell electrons to ionize, and thus the ionization energy decreases down a group. It is also known as screening.