Which species contains the greatest number of unpaired electrons ?
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Answer: B. 7Y
Explanation
Nitrogen, with an atomic number of seven, has an electronic configuration of one s squared two s squared two p cubed. Hund rule dictates that electrons occupy degenerate orbitals singly before pairing up together. This configuration gives nitrogen three unpaired electrons located in separate spatial p-orbitals. Atomic number defines the total number of protons and electrons in a neutral ground state atom. Electron filling follows the Aufbau principle, Pauli exclusion principle, and Hund maximum multiplicity rule. Unpaired electrons generate atomic magnetic moments that influence chemical reactivity and spectroscopic properties.
Magnetic resonance imaging technology relies on nuclear and electronic spin properties to image tissues. Spectroscopic techniques measure electronic transitions involving unpaired electrons to study molecular structures. Quantum chemical calculations depend on accurate electron configurations to predict atomic bonding behavior. Carbon with atomic number six has a ground state configuration ending in two p squared with two unpaired electrons. Fluorine with atomic number nine ends in two p five, leaving only one single unpaired electron. Aluminum with atomic number thirteen contains a single unpaired electron in its outer three p subshell.
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