Which of the following elements has the smallest atomic size?
A)Na
B)Ar
C)K
D)Ca
E)Kr

Question

Quizplus · Accepted Answer

In general, as you move from left to right across a period (horizontal row) on the periodic table, the atomic size decreases. This is because the number of protons in the nucleus increases, drawing the electrons in closer to the nucleus and making the atom smaller. Ar (argon) is in Group 18 and Period 3, and is located to the right of Na (sodium), K (potassium), and Ca (calcium), all of which are in Period 4. Kr (krypton) is also in Group 18, but is located to the right of Ar in Period 4. Therefore, of the given choices, Ar has the smallest atomic size because it is located furthest to the right on the periodic table.

Which of the Following Elements Has the Smallest Atomic Size