Multiple Choice
Which of the following is the correct electron configuration for the N^{3-} anion?
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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 calcium (atomic number 20)?
A
1s^2 2s^2 2p^6 3s^2 3p^6 3d^2
B
1s^2 2s^2 2p^6 3s^2 3p^6 4p^2
C
1s^2 2s^2 2p^6 3s^2 3p^4 4s^2
D
1s^2 2s^2 2p^6 3s^2 3p^6 4s^2
Verified step by step guidance1
Identify the atomic number of calcium, which is 20. This means calcium has 20 electrons to be placed in its electron configuration.
Recall the order in which electron orbitals are filled according to the Aufbau principle: 1s, 2s, 2p, 3s, 3p, 4s, then 3d, and so on.
Fill the orbitals with electrons following this order until all 20 electrons are assigned: 1s can hold 2 electrons, 2s holds 2, 2p holds 6, 3s holds 2, 3p holds 6, and 4s holds 2.
Write the electron configuration by listing each filled orbital with its corresponding number of electrons, for example, $1s^2 2s^2 2p^6 3s^2 3p^6 4s^2$.
Compare the given options to this configuration and select the one that matches the correct filling order and total number of electrons for calcium.
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