Draw the geometrical atomic structure representing the electronic configuration of atoms of elements of
[a] Period- 2
[i] group 14[IVA] - carbon [at. no. 6]
[ii] group 15[VA] - nitrogen [at. no. 7]
[iii] group 16 [VIA] - oxygen [at. no. 8]

[b] Period - 3
[i] group 1[IA] - sodium[at. no. 11]
[ii] group 2[IIA] - magnesium[at. no. 12]
[iii] group 17[VIIA] - chlorine[at. no. 17]

[c] Period - 4
[i] group 2[IIA] - calcium [at. no. 20].