The electronic configuration is 1s² 2s² 2p⁵. The 1s orbital is filled with 2 electrons (paired). The 2s orbital is filled with 2 electrons (paired). The 2p subshell consists of three orbitals (2px, 2py, 2pz). It contains 5 electrons. According to Hund's rule, electrons first singly occupy each orbital in a subshell before pairing up. So, the 5 electrons in the 2p subshell are distributed as follows: one in 2px, one in 2py, one in 2pz (3 unpaired), then pairing occurs: one more in 2px, one more in 2py. Distribution: 2px² 2py² 2pz¹ This results in two paired orbitals (2px, 2py) and one orbital (2pz) with a single unpaired electron. Therefore, there is 1 unpaired electron.
The electronic configuration of an atom is 1s², 2s², 2p⁵. The number of unpaired electrons in this atom are
Asked in PPSC CS Prelims 2015 · Topic: Atomic Structure (Electronic Configurations of Multi-electron Atoms and Ions)
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