According to Hund's rule, electrons entering a set of degenerate orbitals will
Correct answer: B. occupy separate orbitals with parallel spins before pairing
- A. pair up in the first orbital before entering the next
- B. occupy separate orbitals with parallel spins before pairing
- C. occupy the orbital of highest energy first
- D. always pair with opposite spins immediately
Explanation
Electrons repel one another, so they spread across orbitals of equal energy singly and with parallel spins before any orbital takes a second electron. This is why nitrogen, with three 2p electrons, has three unpaired electrons rather than one pair and one single. Filling lowest energy orbitals first is the Aufbau principle, a separate rule.
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About Electronic Configuration
Electronic configuration describes how electrons occupy shells, subshells and orbitals around an atom. Questions use the Aufbau principle, Pauli exclusion principle and Hund's rule to write configurations, identify valence electrons, form ions and explain periodic trends, including common exceptions such as chromium and copper.
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