The element with the highest value of ionization potential is

The first ionisation energy of lithium $(Li)$ will be

Which of the following species has the highest ionisation potential?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A:$ The first ionisation enthalpy decreases across a period.
Reason $R:$ The increasing nuclear charge outweighs the shielding across the period.
In the light of the above statements,choose the most appropriate from the options given below:

Discuss the trend of the first ionisation enthalpy in the same period and explain why it occurs.

The set representing the correct order of first ionisation potential is