if you mean lewis dot symbol you need a nuclide you get the number of proton (z) its equal to electrons since the atom is nutral then you make the elctron configuraion after that you take the number of electrons on the outer energy level( ex:k²L² in this case its the 2 on the L)and if you have 7 electrons and the atom is nitrogen so it becomes
_
:N:
.
Hope that helped
