Multiple Choice
Which of the following represents the correct electron configuration for a neutral beryllium (Be) atom?
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 4s^2 3d^6
B
1s^2 2s^2 2p^6 3s^2 3p^6 3d^6 4s^1
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^1 3d^7
D
1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2
Verified step by step guidance1
Identify the atomic number of iron (Fe), which is 26. This means a neutral Fe atom has 26 electrons to arrange in orbitals.
Recall the order of orbital filling based on the Aufbau principle: $1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d$.
Fill the orbitals in order with electrons, remembering that the 4s orbital fills before the 3d orbital because it is lower in energy for neutral atoms.
Distribute the 26 electrons as follows: 2 in $1s$, 2 in $2s$, 6 in $2p$, 2 in $3s$, 6 in $3p$, 2 in $4s$, and the remaining 6 in $3d$ orbitals.
Write the electron configuration as $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6$, which corresponds to the correct ground-state configuration for neutral iron.
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