Question

Calcium (Ca) has an atomic number of 20. What is calcium's ground-state electron configuration?

Answer 1

I belive the answer is C. 1s2 2s2 2p6 3s2 3p6 4s2

Electron configuration are used to tell the distribution of electrons of an atom or molecule. The electron configuration order should follow a specific path. You will found some similarity of the rule with the number of row in the periodic table. After the electrons fill 3P, the electron should fill 4S before it go to 3D.

Answer 2

Answer: Option (c) is the correct answer.

Explanation:

Calcium is a group 2 element and it lies in period 4 and group 2.

Atomic number of calcium is 20 and its electronic distribution is 2, 8, 8, 2. That is, in ground state there are 20 electrons present in a calcium atom.

It's electronic configuration is as follows.

                $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$

Thus, we can conclude that calcium's ground-state electron configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{2}$.