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Suppose a nitrogen atom were imagined to have the configuration 1s⁷. This would place all electrons in the 1s orbital and, because they would be nearer the nucleus, would seem to have lower energy than the normal ground-state arrangement 1s² 2s² 2p³. However, such a configuration does not occur. Which principle does it break?

1. Heisenberg uncertainty principle
2. Hund's rule
3. Pauli exclusion principle
4. Bohr's postulate of stationary orbits

Correct answer: Pauli exclusion principle

Solution

The Pauli exclusion principle states that no two electrons can occupy the same quantum state within a quantum system simultaneously. In the hypothetical configuration 1s⁷, all seven electrons would be in the same 1s orbital, violating this principle.

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