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Ch 41: Quantum Mechanics II: Atomic Structure
Young & Freedman Calc - University Physics 14th Edition
Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610Not the one you use?Change textbook
Chapter 41, Problem 7a

Consider an electron in the NN shell. What is the smallest orbital angular momentum it could have?

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Understand the quantum number system: The N shell corresponds to the principal quantum number \( n = 4 \). The orbital angular momentum of an electron is determined by the azimuthal quantum number \( l \), which can take integer values from \( 0 \) to \( n-1 \).
Identify the smallest possible value of \( l \): Since \( l \) starts at \( 0 \), the smallest orbital angular momentum corresponds to \( l = 0 \).
Recall the formula for orbital angular momentum: The magnitude of the orbital angular momentum is given by \( \sqrt{l(l+1)} \hbar \), where \( \hbar \) is the reduced Planck's constant.
Substitute \( l = 0 \) into the formula: When \( l = 0 \), the orbital angular momentum becomes \( \sqrt{0(0+1)} \hbar = 0 \).
Conclude: The smallest orbital angular momentum an electron in the N shell can have is \( 0 \), which occurs when \( l = 0 \).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Orbital Angular Momentum

Orbital angular momentum is a measure of the rotational motion of an electron around the nucleus of an atom. It is quantized and can be expressed using the formula L = mvr, where L is the angular momentum, m is the mass of the electron, v is its velocity, and r is the radius of its orbit. In quantum mechanics, the angular momentum is also described by quantum numbers.
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Quantum Numbers

Quantum numbers are sets of numerical values that describe the unique quantum state of an electron in an atom. The principal quantum number (n) indicates the energy level and size of the orbital, while the azimuthal quantum number (l) determines the shape of the orbital. For an electron in the N shell, n = 4, and the smallest value of l is 0, corresponding to an s orbital.
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Quantization of Angular Momentum

In quantum mechanics, angular momentum is quantized, meaning it can only take on specific discrete values. The quantization condition for orbital angular momentum is given by L = √(l(l+1))ħ, where l is the azimuthal quantum number and ħ is the reduced Planck's constant. For the smallest orbital angular momentum, we use l = 0, leading to L = 0, indicating no angular momentum for that state.
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