## Chemistry: The Central Science (13th Edition)

Published by Prentice Hall

# Chapter 7 - Periodic Properties of the Elements - Exercises: 7.15a

#### Answer

Both Na and K are expected to experience the effective nuclear charge $Z_{eff}=+1$

#### Work Step by Step

1) $Na$: The nuclear charge of Na is $Z=+11$. There are 10 core electrons and 1 valence electrons. Each core electron contributes 1.00 and each valence electron contributes 0.00 to the screening constant. Therefore, $S=10\times1.00+1\times0.00=10$ Therefore, the effective nuclear charge of Na is $$Z_{eff}=Z-S=+11-10=+1$$ 2) $K$: The nuclear charge of K is $Z=+19$. There are 18 core electrons and 1 valence electrons. Each core electron contributes 1.00 and each valence electron contributes 0.00 to the screening constant. Therefore, $S=18\times1.00+1\times0.00=18$ Therefore, the effective nuclear charge of K is $$Z_{eff}=Z-S=+19-18=+1$$

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