Multiple Choice
What is the ground-state electron configuration of phosphorus (P), atomic number 15?
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9. Electrons in Atoms and the Periodic Table
The Electron Configuration (Simplified)
Multiple Choice
What is the ground-state electron configuration of the ion (cobalt(II))?
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Verified step by step guidance1
Identify the atomic number of cobalt (Co), which is 27, meaning a neutral cobalt atom has 27 electrons.
Write the ground-state electron configuration for neutral cobalt: start with the noble gas core [Ar], then add the electrons in the 4s and 3d orbitals. This gives [Ar] 4s\^2 3d\^7.
Since the ion is Co\^{2+}, it has lost 2 electrons compared to the neutral atom. Determine from which orbitals these electrons are removed first. Remember that electrons are removed first from the outermost shell, which is the 4s orbital before the 3d orbital.
Remove 2 electrons from the 4s orbital of the neutral cobalt configuration, resulting in the electron configuration for Co\^{2+} as [Ar] 3d\^7.
Confirm that the final electron configuration for Co\^{2+} is [Ar] 3d\^7, which matches the expected ground-state configuration for the cobalt(II) ion.
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