Question

which diagram below correctly obeys all rules of orbital notation? *
diagram a: 1s with two up arrows, 2s with two up arrows, 2p with three boxes: first box two up arrows, second and third boxes one up arrow each
diagram b: 1s with up and down arrows, 2s with up and down arrows, 2p with three boxes: first box two up arrows, second and third boxes one up arrow each
diagram c: 1s with up and down arrows, 2s with up and down arrows, 2p with three boxes: first box up and down arrows, second and third boxes one up arrow each
diagram d: 1s with one up arrow, 2s with one up arrow, 2p with three boxes each with up and down arrows
options: diagram a, diagram b, diagram c, diagram d

Explanation:

To determine the correct orbital notation diagram, we use the rules of electron configuration:

1. Pauli Exclusion Principle: Each orbital can hold a maximum of 2 electrons with opposite spins (↑↓).
2. Aufbau Principle: Electrons fill lower - energy orbitals (1s < 2s < 2p) first.
3. Hund’s Rule: Electrons fill degenerate (same - energy) orbitals (e.g., 2p) singly with parallel spins before pairing.

• Diagram A: The 1s and 2s orbitals have 2 electrons with parallel spins (violates Pauli Exclusion Principle, as spins should be opposite in a filled orbital).
• Diagram B: The 2p orbital on the left has 3 electrons (violates Pauli Exclusion Principle, as an orbital can hold at most 2 electrons).
• Diagram C:
• 1s: 2 electrons (↑↓, follows Pauli).
• 2s: 2 electrons (↑↓, follows Pauli).
• 2p: Three degenerate orbitals. The first 2p orbital has 2 electrons (↑↓), and the other two 2p orbitals have 1 electron each (↑) with parallel spins (follows Hund’s Rule and Aufbau Principle).
• Diagram D: Electrons fill 2p orbitals before 2s is fully filled (violates Aufbau Principle, as 2s is lower energy than 2p and should be filled first).

Answer:

Diagram C