Question

which diagram shows a pair of electrons that have opposite spins?
○ ↑↓
○ ↑ ↓
○ ↑ ↑
○ ↑↑

Explanation:

To determine which diagram shows a pair of electrons with opposite spins, we recall the Pauli Exclusion Principle and electron spin representation. Electron spin is represented by arrows: upward (↑) for one spin and downward (↓) for the opposite spin. For a pair of electrons in the same orbital (represented by the same box), they must have opposite spins (paired electrons). Let's analyze each option:

1. The first option (↑↓) shows two electrons in the same box with one arrow up and one down, indicating opposite spins.
2. The second option (↑ in one box and ↓ in another) shows electrons in different orbitals (different boxes), so this is about electrons in separate orbitals, not a paired pair in the same orbital.
3. The third option (↑ and ↑) shows two electrons with the same spin (both up) in different orbitals, which is not a pair with opposite spins.
4. The fourth option (↑↑) shows two electrons with the same spin (both up) in the same orbital, which violates the Pauli Exclusion Principle for paired electrons.

So the diagram with a pair of electrons (in the same orbital) having opposite spins is the one with ↑↓ in the same box.

Answer:

The first option (the box with \(\boldsymbol{\uparrow\downarrow}\))