Electronic configuration of calcium atom can be written asSelect answersA [Ne], 4p2 B [Ar], 4s2 C [Ne], 4s2 D [Kr], 4p2

The electronic configuration of a calcium atom is written as [Ar], 4s2. Therefore, the correct answer is B [Ar], 4s2.

Here's the step-by-step explanation:

1. The atomic number of calcium is 20. This means it has 20 electrons in its neutral state.

2. The electron configuration is the distribution of electrons of an atom or molecule in atomic or molecular orbitals.

3. The electron configuration is based on the principle of increasing orbital energy from the Aufbau principle, with electrons added one at a time to the lowest energy orbitals first (the 1s orbital), then in increasing energy order.

4. The first 18 electrons will fill the 1s, 2s, 2p, 3s, 3p, and 4s orbitals. This configuration corresponds to the electron configuration of Argon ([Ar]).

5. The remaining 2 electrons will go into the next lowest energy orbital, which is the 4s orbital.

6. Therefore, the electron configuration of a calcium atom is [Ar], 4s2.