Question

Electronic configuration of calcium is?
A. $(Ar)4s^2$
B. $(Ne)3s^2$
C. $(Ar)4s^2$
D. $(Kr)4s^2$

Answer 1

Hint: There are two different ways to write the electronic configuration of the elements. First one is like an expanded electron configuration containing all the orbitals clearly. The second one is the short form contains a noble gas and the valence electrons in the orbital.

Complete answer:
- In the question it is given what is the electronic configuration of calcium.
- The element calcium belongs to II A group in s-block.
- The atomic number of calcium is 20 means the number of protons are 20.
- We know that the number of protons and electrons are the same, so the number of protons and electrons in calcium is 20.
- Means the number of electrons present in the calcium are 20.
- The general electronic configuration of calcium is as follows.
$$1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^2$$
- We can write electronic configuration of calcium in another form also by taking first 18 electrons in the form of Argon (it is the nearest noble gas which contains 18 electrons, the electronic configuration of Argon is $1s^{2}2s^{2}2p^{6}3s^{2}3s^6$ .
- Then the electronic configuration of calcium is $(Ar)4s^2$ .

- So, the correct option is A.

Note: Calcium contains two valence electrons in its valence shell. To get inert gas configuration calcium loses it’s two valence electrons and gets the electronic configuration of the Argon (Inert gas). So, the stable oxidation state of calcium is +2. The electrons are going to fill in the order of 1s, 2s, 2p, 3s, 3p, 4s, 4p and etc.