2.13—Orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin

Know that orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin.

Use —orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin to connect the rule to the data and decision in the question.

This matters because —orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply —orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: —Orbitals in sub-shells: i each take a single electron before pairing up ii pair up with two electrons of opposite spin is not a universal recommendation. Check the syllabus scope, assumptions, units and the limits of the evidence before generalising.