Chemistry: The Central Science (13th Edition)

Published by Prentice Hall
ISBN 10: 0321910419
ISBN 13: 978-0-32191-041-7

Chapter 7 - Periodic Properties of the Elements - Exercises: 7.32a


$K^+$ ion is smaller than $Cl^-$ ion.

Work Step by Step

Both $Cl^-$ and $K^+$ have 18 electrons, so their electron-electron repulsions are quite the same. However, $Cl^-$ has a nuclear charge of $17+$, while $K^+$ has a nuclear charge of $19+$. Therefore, the attraction of the $K^+$ nucleus is greater than that of the $Cl^-$ nucleus. That means the electrons of $K^+$ are more attracted and closer to the nucleus than those of $Cl^-$. Therefore, $K^+$ ion is smaller than $Cl^-$ ion.
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