## Chemistry: The Molecular Science (5th Edition)

Published by Cengage Learning

# Chapter 2 - Chemical Compounds - Questions for Review and Thought - Topical Questions - Page 90b: 24b

#### Answer

$^{39}_{18}Ar$

#### Work Step by Step

Recall, the superscript gives the number of protons plus the number of neutrons, so add the number of protons and the number of neutrons to get this number. The subscript, contrarily, indicates the number of protons present. We find the number for the superscript and then complete the entire symbol. Mass number = 18 protons + 21 Neutrons = 39 This gives: $^{39}_{18}Ar$

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