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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 7d

Consider an electron in the NN shell. What is the largest spin angular momentum this electron could have in any chosen direction? Express your answers in terms of \(\hslash\) and in SI units.

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1
Identify the quantum number associated with spin angular momentum. The spin quantum number (s) for an electron is always 1/2, which is a fundamental property of electrons.
The spin angular momentum in any chosen direction is given by the formula: Sz = msħ, where ms is the spin magnetic quantum number and ħ is the reduced Planck's constant.
For an electron, the possible values of ms are +1/2 and -1/2. The largest spin angular momentum in any chosen direction corresponds to ms = +1/2.
Substitute ms = +1/2 and ħ = 1.0545718 × 10-34 \(\text{ J·s}\) into the formula to express the largest spin angular momentum in SI units.
The final expression for the largest spin angular momentum in any chosen direction is: Sz = (1/2) × ħ, which can be evaluated numerically if needed.

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Key Concepts

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

Spin Angular Momentum

Spin angular momentum is an intrinsic form of angular momentum carried by particles, such as electrons. It is quantized and can take on values that are integer or half-integer multiples of the reduced Planck constant (ħ). For electrons, the spin quantum number is 1/2, leading to two possible spin states: +ħ/2 and -ħ/2, which correspond to 'spin up' and 'spin down' respectively.
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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, while the azimuthal quantum number (l) describes the shape of the orbital. The magnetic quantum number (m_l) specifies the orientation of the orbital, and the spin quantum number (m_s) indicates the direction of the electron's spin, which is crucial for determining the total angular momentum.
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Units of Angular Momentum

Angular momentum in quantum mechanics is typically expressed in terms of the reduced Planck constant (ħ), where ħ = h/(2π) and h is Planck's constant. In SI units, angular momentum is measured in joule-seconds (J·s). For an electron, the maximum spin angular momentum can be calculated as S = m_s * ħ, where m_s can take values of ±1/2, leading to a maximum value of ħ/2 in the chosen direction.
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