Multiple Choice
Which of the following is the correct orbital notation for boron (atomic number 5)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the correct electron configuration for a neutral iron (Fe) atom?
A
1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^8
C
1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^2
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6
Verified step by step guidance1
Identify the atomic number of iron (Fe), which is 26. This means a neutral iron atom has 26 electrons to be placed in orbitals.
Recall the order of orbital filling based on the Aufbau principle: electrons fill orbitals starting from the lowest energy level to higher ones, following the sequence 1s, 2s, 2p, 3s, 3p, 4s, then 3d.
Fill the orbitals with electrons according to their capacities: 1s can hold 2, 2s can hold 2, 2p can hold 6, 3s can hold 2, 3p can hold 6, 4s can hold 2, and 3d can hold 10 electrons.
Add electrons in order until all 26 electrons are assigned: fill 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, then 4s^2, and finally place the remaining electrons in 3d orbitals.
Verify the final electron configuration matches the total number of electrons (26) and follows the correct order: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6$.
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