How To Determine Formal Charge On An Atoms ~ Formal charge in chemistry is a calculation that can be used on lewis structure to determine the charge of the atoms that form an ionic or covalent bond. The formal charge can be used in determining which structures are more stable. When there are several possible Lewis structures that can be made, then the structure with the smallest formal charge (close to zero) is selected.
In some molecules, some elements show a covalent bond with an unusual amount. If in drawing Lewis structures correctly of these compounds is not possible, unless we provide an electrostatic charge which is called formal charge to some elements in the molecule.Calculate The Formal Charge Of An Atom
The equation is as shown below ;
Formal Charge =
Number of valence electrons - [ Number of unshared electrons + 1/2 (Number of shared electrons) ]
Note :
- Number of Unshared Electrons = How many unpaired electrons (calculated individually and not as a "pairs")
- Number of Shared Electrons = How many electrons are paired (calculated individually and not as a "paired")
Example,
#Calculating Formal Charge of CH₃ – N(a) ≡ N(b) :
As an example, I will calculate the formal charge of N(a), as shown below ;
Then, I will calculate the formal charge of N(b), as shown below ;
Henceforth, the method of calculating the other atoms such as H atoms and C atoms are the same as above.
FC of H = 1 – [ 0 + 1/2 ( 2 ) ] = 0
FC of C = 4 – [ 0 + 1/2 ( 8 ) ] = 0
FC of Na = 5 – [ 0 + 1/2 ( 8 ) ] = + 1
FC of Nb = 5 – [ 2 + 1/2 ( 6 ) ] = 0
Therefore,
#Calculating Formal Charge of CH3NO
FC of H = 1 – [ 0 + 1/2 ( 2 ) ] = 0
FC of C = 4 – [ 0 + 1/2 ( 8 ) ] = 0
FC of N = 5 – [ 2 + 1/2 ( 6 ) ] = 0
FC of O = 6 – [ 4 + 1/2 ( 4 ) ] = 0
Therefore,
#Calculating Formal Charge of NCS⁻
FC of N = 5 – [ 2 + 1/2 ( 6 ) ] = 0
FC of C = 4 – [ 0 + 1/2 ( 8 ) ] = 0
FC of S = 6 – [ 6 + 1/2 ( 2 ) ] = -1
Therefore,
That is the way to determine the formal charge of an atom in a molecule. Pretty easy isn't it?
No comments:
Post a Comment