Answer 1

1. Across a period, the screening effect is the same, and the effective nuclear charge increases.
2. As a result, the outer electron is held more tightly, and hence, the ionization enthalpy increases across a period.
3. Inert gases are present on the extreme right of the periodic table i.e., in group 18. Also, inert gases have stable electronic configurations i.e., complete octet or duplet. Due to this, they are extremely stable and it is very difficult to remove electrons from their valence shell.
   Hence, inert gases have exceptionally high ionization potential.