The Lewis diagram is a structural formula that shows the bonds that exist between the atoms of a molecule and the pair of solitary electrons that may occur. It is a very appropriate and simple diagram of ions and compounds, which make a precise calculation of electrons possible, forming an important, relative and balanced base.
The Lewis diagram is used to determine the amount of valence electrons of an element that is in contact with others or between elements of the same species, constituting bonds that could be simple, double or triple, and then each of them, be in each covalent bond.
The Lewis diagram presents symbols where the electrons of the valence shell that are embedded within an atom are symbolized by points located around the sign of the element.
To make this diagram, certain requirements must be met:
- The central atom must be chosen, which will generally be the least electronegative.
- Around the central atom, the others are located and in the most proportionate way possible.
- The absolute number of valence electrons in each of the atoms must be calculated, adding net length to it, if there is one. For example, if the net charge is -2, two electrons will be added to it, now, if the total charge is +1, one electron must be reduced.
- A junction must be drawn between each pair of atoms that maintain contact. Designating each link a pair of electrons that will then be deducted from the global amount.
- It begins with the ligands and ends in the central atom, to designate the electrons that remain, in pairs, to each of the atoms until the layer is closed.
- Determine the formal charge of each atom, starting with the central one. The formal charge represents a hypothetical charge, which each atom presents within the diagram and is produced by the disparity between the valence electrons of the free atom and those designated to the structure of said atom.
Now, if the formal charge of the atom is equivalent to the net charge of the molecule or is negative, then the diagram is valid and at this point the process ends.
- If the opposite happens, the diagram must be changed, creating a double bond around the central atom.
