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 - Page 366: 8.142

Answer

Please see the work below.

Work Step by Step

We know that $He^+$ has only one electron hence it has no shielding. We also know that if there is greater attraction between nucleus and the lone electron than radius will be less than that of hydrogen. Thus, $I_2(He)>2I(H)$.
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