Multiple Choice
How many p electrons are present in a neutral atom of antimony (Sb)?
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10. Periodic Properties of the Elements
The Electron Configuration
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Which of the following is the electron configuration of a neutral 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 3d^8 4s^2
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^8
Verified step by step guidance1
Step 1: Determine the atomic number of the neutral Fe (iron) atom. The atomic number tells you the total number of electrons in the atom. For Fe, the atomic number is 26, so there are 26 electrons to place in orbitals.
Step 2: Recall the order in which electron orbitals are filled according to the Aufbau principle. The filling order up to Fe 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: Add the electrons stepwise until you reach 26 total electrons. After filling 1s, 2s, 2p, 3s, and 3p orbitals, you will have placed 18 electrons. Next, fill the 4s orbital with 2 electrons, bringing the total to 20 electrons.
Step 5: Place the remaining 6 electrons in the 3d orbital, since 3d comes after 4s in filling order for neutral atoms. This results in the electron configuration: $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^6$.
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