Chemistry 12th Edition

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

Chapter 2 - Atoms, Molecules, and Ions - Questions & Problems - Page 68: 2.14

Answer

number of neutrons $=$ mass number $-$ number of protons $=239-94=145$

Work Step by Step

Strategy: The 239 in Pu- 239 is the mass number. The mass number $(A)$ is the total number of neutrons and protons present in the nucleus of an atom of an element. You can look up the atomic number (number of protons) on the periodic table. Solution: mass number $=$ number of protons $+$ number of neutrons number of neutrons $=$ mass number $-$ number of protons $=239-94=145$
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