Multiple Choice
What is the primary difference between the 1s and the 2s orbitals?
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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 gallium (Ga)?
A
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^1
B
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 4p^1 3d^{10}
C
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^8 4p^3
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^{10} 4p^3
Verified step by step guidance1
Identify the atomic number of gallium (Ga), which is 31. This means gallium has 31 electrons to place in its electron configuration.
Recall the order of filling orbitals according to the Aufbau principle: $1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d \rightarrow 4p$.
Fill the orbitals in order with the correct number of electrons until you reach 31 electrons: $1s^2$, $2s^2$, $2p^6$, $3s^2$, $3p^6$, $4s^2$, $3d^{10}$, and then place the remaining electron(s) in the $4p$ orbital.
Remember that the $3d$ orbitals fill after the $4s$ orbital, so $3d^{10}$ comes before $4p$ electrons in the configuration.
Compare the given options to the correct order and electron counts in each subshell to determine which matches the proper electron configuration for gallium.
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