Electronic configuration of calcium atom can be written as

The electronic configuration of a calcium atom is 2, 8, 8, 2.

Here's the step-by-step process:

1. Identify the atomic number of calcium. The atomic number of calcium is 20, which means it has 20 electrons in its neutral state.

2. The first two electrons will go in the 1s orbital. The 1s orbital can hold up to two electrons, so it is now full. The configuration is now 1s².

3. The next two electrons will go in the 2s orbital. The 2s orbital can also hold up to two electrons. The configuration is now 1s² 2s².

4. The next six electrons will go in the 2p orbital. The 2p orbital can hold up to six electrons. The configuration is now 1s² 2s² 2p⁶.

5. The next two electrons will go in the 3s orbital. The 3s orbital can hold up to two electrons. The configuration is now 1s² 2s² 2p⁶ 3s².

6. The next six electrons will go in the 3p orbital. The 3p orbital can hold up to six electrons. The configuration is now 1s² 2s² 2p⁶ 3s² 3p⁶.

7. The next two electrons will go in the 4s orbital. The 4s orbital can hold up to two electrons. The configuration is now 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

8. The remaining two electrons will go in the 4s orbital. The configuration is now 1s² 2s² 2p⁶ 3s² 3p⁶ 4s².

So, the electronic configuration of a calcium atom is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² or simply 2, 8, 8, 2.