Let's make some more molecules

Nitrogen Atom

The electronic configuration of a molecule of nitrogen which is like the electronic configuration of a neon atom.


Water molecule

Formation of water molecule 
 

When two hydrogen atoms, which have an electron each in their outermost shell, come close to two atoms of oxygen, one atom hydrogen gives its single electron to one atom of oxygen and completes its electronic configuration and the other Hydrogen atom also gives its single electron to the other atom of oxygen. Now these two atoms of oxygen which already have a hydrogen atom, share an electron each and complete their outermost shell with eight electrons. As a result we get one molecule of hydrogen peroxide (H2O2).

Now let us talk about the Ammonia molecule. We know that the nitrogen atom has 5 electrons in the outermost shell. It requires three more electrons to get the total of eight in the outermost shell. It fulfils this requirement with three electrons from three Hydrogen atoms - that is, one from each. It shares one electron each with each atom of hydrogen, which makes two electrons in the outermost shells of the hydrogen atoms. The outermost shell of Nitrogen also gets eight and a molecule of Ammonia is formed.

Ammonia Molecule

To do: 
Now you all can try and make bigger molecules like methane (CH₄), carbon tetrachloride (CCl₄), ethane (C₂H₆) with the help of these dot or crosses diagrams. Whle constructing them, you need to think which inert gas' electronic configuration are the molecules resembling? You need to keep in mind that whenever you make molecules by sharing, the outermost shell should have eight electrons (Hydrogen should have two).
This will strengthen your understanding of sharing of electrons.