Question

Which element has the highest $1^{st}$ ionization energy?

• A. $K$
• B. $Li$
• C. $H$
• D. $Na$
• E. $Rb$

Answer 1

The correct option is C $H$

The value of IE decreases down the group with the increasing ease to remove electron due to increase in size. All given elements belong to the same group (IA) and Hydrogen (H) is top most. Thus ($H$) has the highest value of first IE.