Chemistry: The Molecular Science (5th Edition)

Published by Cengage Learning
ISBN 10: 1285199049
ISBN 13: 978-1-28519-904-7

Chapter 18 - Nuclear Chemistry - Questions for Review and Thought - General Questions - Page 817d: 74c

Answer

$^{4}_{2}He$

Work Step by Step

Let the missing reactant be $\,^{A}_{Z}X$ where $X$ is the symbol, $Z$ is the atomic number and $A$ is the mass number. As the sum of masses on both sides must be equal: $253+A=256+1\implies A=257-253=4$ As the sum of charges must be equal: $99+Z=101+0$ or $Z=101-99=2$ The symbol of the element with atomic number 2 is $He$. Therefore, the missing reactant is $\,^{4}_{2}He$.
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