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: 7.15b

Answer

Both outermost electrons in Na and K experience an effective nuclear charge of $2.2+$.

Work Step by Step

1) $Na$: The nuclear charge of $Na$ is $Z=11+$. The outermost electrons of Na is in the $n=3$ shell. Na has: - 2 electrons in the $n=1$ shell, each of which contributes 1.00 to $S$. - 8 electrons in the $n=2$ shell, each of which contributes 0.85 to $S$. - 1 valence electron in the $n=3$ shell, but since Slater's rules do not account for the screening effect of 1 electron to itself, this electron does not contribute to $S$. That means $S=2\times1+8\times0.85=8.8$ Therefore, $$Z_{eff}=Z-S=(11+)-8.8=2.2+$$ 2) $K$: The nuclear charge of $K$ is $Z=19+$. The outermost electrons of K is in the $n=4$ shell. K has: - 2 electrons in the $n=1$ shell, each of which contributes 1.00 to $S$. - 8 electrons in the $n=2$ shell, each of which contributes 1.00 to $S$. - 8 electrons in the $n=3$ shell, each of which contributes 0.85 to $S$. - 1 electron in the $n=4$ shell. However, Slater's rules do not account for the screenning effect of 1 electron to itself, this electron does not contribute to $S$. That means $S=2\times1+8\times1+8\times0.85=16.8$ Therefore, $$Z_{eff}=Z-S=(19+)-16.8=2.2+$$
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.