Atoms of which of the following elements are smallest?
A) Rb
B) K
C) Na
D) None, they are all the same size.

Question

Quizplus · Accepted Answer

The size of an atom generally decreases from left to right across a period in the periodic table due to increased nuclear charge. Therefore, sodium (Na) will have a larger atomic radius than potassium (K) and rubidium (Rb) as they are to the right of Na in the same period. So, out of the given options, the atom of sodium (Na) will be the largest and thus the atoms of Rb and K will be smaller than that of Na. Therefore, choice C is the best answer.

Atoms of Which of the Following Elements Are Smallest