Multiple Choice
In atomic theory, what term best describes the region of space around a nucleus where there is a high probability of finding an electron?
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9. Electrons in Atoms and the Periodic Table
Electronic Structure: Orbitals
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
In its ground-state electron configuration, how many unpaired electrons are present in a neutral phosphorus atom (atomic number )?
A
5
B
3
C
1
D
2
Verified step by step guidance1
Identify the atomic number of phosphorus, which is 15. This means a neutral phosphorus atom has 15 electrons.
Write the ground-state electron configuration for phosphorus by filling orbitals in order of increasing energy: 1s, 2s, 2p, 3s, and 3p.
The electron configuration will be: \$1\,s^2\,2\,s^2\,2\,p^6\,3\,s^2\,3\,p^3$.
Focus on the outermost electrons in the 3p subshell, which has 3 electrons. According to Hund's rule, these electrons will occupy separate orbitals with parallel spins.
Count the number of unpaired electrons in the 3p subshell. Since there are 3 electrons in 3 separate p orbitals, the number of unpaired electrons is 3.
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