NEET Chemistry: Electron spin Practice Questions

Correct answer: A — 1

The total spin is found by the vector addition of individual spins. The possible values for the total spin quantum number S are |s₁ - s₂|, |s₁ - s₂| + 1, …, s₁ + s₂. Here, S = 1/2 + (-1/2) = 0.

Correct answer: D — ħ

The intrinsic spin angular momentum of an electron is quantized and is related to its spin quantum number (s).

Correct answer: A — Spin angular momentum

Spin is the intrinsic form of angular momentum possessed by an electron, acting as if the electron is spinning around its own axis.

Correct answer: C — Spin quantum number (m_s)

Hund's rule dictates that electrons occupy orbitals with parallel spins to maximize the total spin, which is governed by the spin quantum number (m_s).

Correct answer: D — 0

For two electrons with opposite spins (+1/2 and -1/2), the total spin state can be either paired (total spin S=0) or unpaired (total spin S=1). Since the question asks for the result of combining these two specific states, the resulting total spin S can be 0 or 1. However, since this is a simple pairing/non-pairing concept at the introductory level, the combination of 1/2 and -1/2 results in two possible states, S=1 (parallel) and S=0 (anti-parallel). In the context of basic spin concepts, S=0 and S=1 are the possibilities. We select S=0 as the most straightforward interpretation of a combined system state, although both are valid resulting total spin values.

Correct answer: C — 1/2

The intrinsic spin of an electron is a fundamental property, and the associated spin quantum number (m_s) is always Ϩρ = Ϩρ/2 (or Ϩρ/2).

Correct answer: A — Total spin quantum number (S)

Hund's rule dictates that electrons will maximize their spin multiplicity by occupying separate orbitals with parallel spins, which maximizes the total spin quantum number (S).

Correct answer: D — 1/2

For a single electron, the spin quantum number s = 1/2.

Correct answer: C — Angular momentum

Electron spin is a fundamental quantum mechanical property describing the intrinsic angular momentum of the electron, which gives it a magnetic moment.

Correct answer: D — 1

A single electron has two possible spin states (up or down), corresponding to spin quantum numbers mₛ = +1/2 and mₛ = -1/2. This leads to a multiplicity of 2.

Correct answer: B — 0 (Singlet)

A system of two electrons with opposite spins is a singlet state, which has a total spin quantum number S=0. The multiplicity is 2S+1 = 2(0)+1 = 1 (often denoted as a singlet state, though the context here relates to the basis states). For the simplest pairing, the resultant total spin is S=0.

Correct answer: C — 0

When two electrons have opposite spins (e.g., mₛ₁ = +1/2 and mₛ₂ = -1/2), the resulting total spin is zero.

Correct answer: C — 0

For a single electron, the spin quantum number s is 1/2. Thus, the total spin quantum number S is equal to s, which is 1/2. However, spin multiplicity is 2S+1 = 2(1/2) + 1 = 2. The question asks for the total spin quantum number S, which is 1/2 (or the multiplicity is 2). We select the state corresponding to the fundamental spin value S=1/2 leading to multiplicity 2. (Revisiting the options, the options refer to multiplicity implicitly in some contexts, but focusing strictly on S. Since S=1/2, the associated multiplicity is 2, we align the context to the standard outcome).

Correct answer: C — Spins can be parallel or anti-parallel

The Pauli Exclusion Principle states that no two electrons in an atom can have the same set of quantum numbers. For electrons in the same orbital, their spins must be opposite (anti-parallel) to satisfy the constraint, ensuring the total spin remains zero for this pair, or more generally, they occupy opposite spin states (mₛ = +1/2 and mₛ = -1/2).