Ch 41: Quantum Mechanics II: Atomic Structure

Young & Freedman Calc - University Physics 14th Edition

Young & Freedman Calc14th EditionUniversity PhysicsISBN: 9780321973610당신이 사용하는 게 아니라요?교과서 변경

Young & Freedman Calc 14th Edition

Ch 41: Quantum Mechanics II: Atomic Structure

문제 7d

41장, 문제 7d

Consider an electron in the $N$ 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.

검증된 단계별 안내

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:

S

_z = m_sħ, where

m

_s is the spin magnetic quantum number and

ħ

is the reduced Planck's constant.

For an electron, the possible values of

m

_s are +1/2 and -1/2. The largest spin angular momentum in any chosen direction corresponds to

m

_s = +1/2.

Substitute

m

_s = +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:

S

_z = (1/2) × ħ, which can be evaluated numerically if needed.

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주요 개념

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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.

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.

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.