can the electronic configuration of ca be 1s2 2s2 2p6 3s2 3p6 4s1 3d1, why not?

Dear Student

Electronic configuration of Ca is ​1s² 2s² 2p⁶ 3s² 3p⁶ 4s² or [Kr] 4s² 
It is present in the 4th energy level of the periodic table and lies in the 2nd group. Since, the first two groups of the periodic table represent the 's' orbital group, therefore the electronic configuration of calcium should end with 's' group only. 
So, the electronic configuration of Ca is the one described above and not ​1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹.

Regards