AIIMS 2014 Chemistry Atomic Structure MCQ Question

The ionization potential (IP) of potassium (K) is lower than that of sodium (Na) because K is located further down the alkali metal group in the periodic table. As you move down a group, the outermost electron is farther from the nucleus and experiences greater shielding from inner electrons, making it easier to remove and resulting in a lower ionization energy. Therefore, the IP of K is approximately 4.4 eV, making option B the correct answer.