University Physics with Modern Physics (14th Edition)

Published by Pearson
ISBN 10: 0321973615
ISBN 13: 978-0-32197-361-0

Chapter 41 - Quantum Mechanics II: Atomic Structure - Problems - Exercises - Page 1402: 41.13

Answer

As n increases, the maximum L is $\sqrt{(n-1)(n)}\hbar $, which gets closer to the value $n \hbar$ postulated in the Bohr model.

Work Step by Step

The maximum orbital angular momentum for a given n occurs for $l=n-1$. We also know that $L=\sqrt{l(l+1)}\hbar$. For n=2, $l_{max}=1$ and $L=\sqrt{l(l+1)}\hbar=\sqrt{2(2+1)}\hbar =1.41\hbar$ For n=20, $l_{max}=19$ and $L=\sqrt{l(l+1)}\hbar=\sqrt{19(19+1)}\hbar =19.49\hbar$ For n=200, $l_{max}=199$ and $L=\sqrt{l(l+1)}\hbar=\sqrt{199(199+1)}\hbar =199.5\hbar$ The trend is clear. As n increases, the maximum L is $\sqrt{(n-1)(n)}\hbar $, which gets closer to the value $n \hbar$ postulated in the Bohr model.
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