All the other elements have less than eight electrons in the outside shell. These electrons can be in the positions of the eight electrons of the noble gases, but there are some suggestions about where they belong. The Group I elements have only one electron in the outer shell, so it really does not matter where the electron dot is placed, over, under, right or left of the element symbol.
 
Group II elements have two electrons. Some authors will place the two electron dots together on any side of the element symbol because the electrons really are in an s subshell together.
 
Some authors will show the electrons separated from each other in any of the two positions with only one electron in each position. The reasoning behind that is that the electrons really do try to move as far away from each other as possible.
 
Boron and the elements below it on the periodic table all have three electrons in the outside shell. These electrons may be grouped as each electron alone in one of the positions around the element symbol or as a group of two (s) electrons in one position and one electron in another. Boron is usually shown with separate electrons because it bonds mostly covalently. Covalent bonds, we know from the shape of molecules, tend to blend the s and p subshells into sp orbitals with one s and one p orbital blended, sp2 orbitals with one s and two p orbitals blended, or sp3 orbitals, using the single s orbital with all three p orbitals. The sp2 orbitals of boron tend to be flat trigonal shape, that is, the bonds are at 120 degrees from each other in a flat circle around the boron atom in the center. The Lewis structure of boron is any of the shapes below.
 
Carbon and the elements below it have four electrons in the outer shell. Carbon and silicon are usually shown in Lewis structures to have four separated electrons, again because these elements bond purely with covalent bonds. The sp3 orbitals of carbon and silicon are tetrahedral in shape.
 
Nitrogen and the elements below it have five electrons in the valence shell, so they must be shown with one pair (anywhere) and three solitary electrons.
 
Oxygen and the elements below it have six valence electrons and so must have two pairs and two solitary electrons.
 
Elements in the halogen group, Group VII, all have seven electrons in the outer shell, so only there are three groups of two and a single electron in the last position.
 
The transition elements and the Lanthanide and Actinide series elements are not often used in the covalent bonds that the Lewis structures usually portray, but these metal elements can be portrayed in this manner using the number of electrons in the outer shell that corresponds with the valence of the element.
There is a difference between the Lewis structure of a compound and the actual 3-D structure. The Lewis structure shows the elements as their symbols, and arranges the bonds (dashes) from each atom at ninety degrees from the symbol. The electrons not in bonds are shown as dots (here, squares) near the element. (See the first drawing.) The 3-D structure attempts to show the actual shape of the molecule.
In the 3-D structure on the right. the electrons that are attached to the nitrogen atom are shown in red. The nitrogen atom is blue, and the hydrogen atoms are black. The bonds from the nitrogen to the hydrogens are also in black. The attempt has been to show the molecule in 3-D, so the bond in back seems to be going into the screen. Each bond has two electrons, so the electrons from all of the participants in this molecule are all accounted for.