Chemistry - PERIODIC TABLE Question with Solution | TestHub

Zinc (Zn) has a higher ionization energy than Gallium (Ga) because the 3d-electrons of Zn shield poorly, increasing the effective nuclear charge on the outer electron. This corresponds to Factor (4): Penetration/poor shielding effect.

For pair (I) Magnesium (Mg) and Aluminum (Al), Mg has a higher ionization energy (IE) than Al ($x>y=P$) because Al's outer electron enters the higher-energy 3p orbital, which is less penetrating and easier to remove.

Therefore, the correct combination is (4), (I), (P).