Chemistry: The Molecular Science (5th Edition)

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

Chapter 5 - Electron Configurations and the Periodic Table - Questions for Review and Thought - Topical Questions - Page 240d: 92


The difference is caused by differences in electron configurations.

Work Step by Step

For oxygen, gaining one electron gives it the electron configuration of a halogen, which is extremely unstable. Thus, the first electron affinity of oxygen is negative. However, the second is positive, for oxygen starts two away from the electron configuration of a noble gas, which is a favorable state.
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