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