Multiple Choice
Which element has the electron configuration 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^4?
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10. Periodic Properties of the Elements
The Electron Configuration
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
How many half-filled orbitals are present in a ground-state bromine (Br) atom?
A
5
B
2
C
3
D
1
Verified step by step guidance1
Identify the atomic number of bromine (Br), which is 35, meaning it has 35 electrons in its neutral ground state.
Write the electron configuration of bromine using the Aufbau principle, filling orbitals in order of increasing energy: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p.
Determine the distribution of electrons in the outermost shell (the valence shell), which for bromine is the 4th shell, specifically the 4p orbitals.
Recall that the 4p subshell has three orbitals, and bromine has 5 electrons in the 4p subshell (since the configuration ends with 4p^5). According to Hund's rule, electrons fill orbitals singly before pairing up.
Count the number of half-filled orbitals in the 4p subshell: with 5 electrons, two orbitals will be fully paired (2 electrons each), and one orbital will have a single unpaired electron, resulting in 1 half-filled orbital.
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