Compared to a potassium atom, a potassium ion has
(1) a smaller radius
(2) a larger radius
(3) fewer protons
(4) more protons
Answer and Explanation: Let's first look at the Periodic Table on the Reference Table to find out what kind of ion potassium has? If we look at the top right of K (potassium), we see the charge is plus 1. Therefore, the ion of potassium has a +1 charge. +1 charge means that potassium atom lost 1 electron. Losing an electron means, a potassium ion has a smaller radius.
P.S. The number of protons gives the identity of the element. Therefore, an atom or an ion of potassium must always have the same number of protons (19).
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