Question

Which of the following elements has the highest ionisation potential?

• A. Li
• B. Na
• C. K
• D. Rb

Answer 1

The correct option is A

Li

The ionisation energy tends to increase as one moves from left to right across a period(with exceptions), because the atomic size decreases due to an increase in the nuclear charge and thus, more energy is required to remove the electron(s).There is an increase in atomic size down the group due to the addition of extra shells. This increase in atomic size overcomes the effect of an increase in the nuclear charge. Therefore, ionisation energy decreases with an increase in atomic size as one move down a group.So, Li has the highest ionisation potential from the given following elements.So, Li has the highest ionisation potential from the given following elements.