Multiple Choice
Which of the following is the correct electron configuration for a neutral sodium (Na) atom?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following represents the complete ground state electron configuration for the iron (Fe) atom?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4d^6
B
1s^2 2s^2 2p^6 3s^2 3p^6 3d^8 4s^2
C
1s^2 2s^2 2p^6 3s^2 3p^6 3d^4 4s^4
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6
Verified step by step guidance1
Step 1: Determine the atomic number of iron (Fe), which tells you the total number of electrons in a neutral atom. Iron has an atomic number of 26, so it has 26 electrons.
Step 2: Recall the order in which electron orbitals are filled according to the Aufbau principle. The filling order up to iron is: 1s, 2s, 2p, 3s, 3p, 4s, then 3d.
Step 3: Fill the orbitals with electrons following the order and the maximum number of electrons each orbital can hold: 1s (2), 2s (2), 2p (6), 3s (2), 3p (6), 4s (2), and 3d (10).
Step 4: Assign the 26 electrons to these orbitals in order: 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6. Note that 4s fills before 3d, but 3d is filled after 4s starts filling.
Step 5: Compare the given options to this configuration. The correct ground state electron configuration for iron is the one that matches 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6.
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