The correct electron configuration for calcium, which is element number 20 in the periodic table, is as follows:
Each atomic orbital can hold a certain number of electrons: up to 2 in an s orbital, 6 in a p orbital, 10 in a d orbital, and 14 in an f orbital. The orbitals are filled in the order of increasing energy, following the Aufbau principle, the Pauli Exclusion Principle, and Hund's Rule.
To determine the electron configuration for calcium:
1. Begin by filling the 1s orbital, which can hold a maximum of 2 electrons.
So, we start with 1s².
2. Then, fill the 2s orbital with its maximum of 2 electrons.
Now we have 1s² 2s².
3. The 2p orbitals come next and can hold a total of 6 electrons.
The configuration is now 1s² 2s² 2p⁶.
4. Following the 2p orbitals, we fill the 3s orbital with 2 electrons.
The electron configuration becomes 1s² 2s² 2p⁶ 3s².
5. After the 3s orbital, we fill the 3p orbitals with 6 electrons.
Updating the configuration to 1s² 2s² 2p⁶ 3s² 3p⁶.
6. Finally, the 4s orbital is filled with 2 electrons because calcium has a total of 20 electrons to account for.
The final correct electron configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².
So, the correct electron configuration for calcium (atomic number 20) is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s², which corresponds to option D.
Options A, B, and C are incorrect:
- Option A is nonsensical as it mentions "2p 2010" which does not correspond to a valid subshell configuration.
- Option B incorrectly lists the 3p⁶ subshell after the 4s² subshell which violates the Aufbau principle (4s is filled before 3d).
- Option C suggests that calcium has electrons in the 3d subshell, which is not the case as calcium only fills up to the 4s subshell.
