Chemistry 12th Edition

Published by McGraw-Hill Education
ISBN 10: 0078021510
ISBN 13: 978-0-07802-151-0

Chapter 8 - Periodic Relationships Among the Elements - Questions & Problems: 8.92

Answer

Please see the work below.

Work Step by Step

As we know that $H^-$ and $He$ are isoelectronic species having two electrons. The nucleus of $H^-$ will attract two electrons less as compared to $He$. Hence, $H^-$ is larger.
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