Chemical Bonding
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Chemical Bonding is a type of force that holds two or more atoms together. It is the attraction between positive nucleus and negative electrons.
2 MAJOR TYPES OF CHEMICAL BONDING
Ionic Bonding
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Simply means transfer of electrons.
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This is a reaction between a metal (cation) and non-metal (anion) where the cation transfers its valence electrons to the anion due to electrostatic force in order to make it stable (octet rule). It is a strong kind of bond.
Example:
Sodium + Chlorine --> Sodium chloride
Covalent Bonding
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Simply means sharing of electrons.
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Covalent bonding is the result of chemical bonding of elements that share pairs of valence electrons. These bonds are usually formed by non-metal elements.
Example:
Hydrogen + Chlorine --> Hydrogen Chloride
Formal Charge
- It is the charge assigned to an atom in a molecule, assuming that electrons in a chemical bond are shared equally between atoms, regardless of relative electronegativity.
The formal charge of any atom in a molecule can be calculated by the following equation:
FC=V – (N + B/ 2)
wherein:
V=no. of valence electrons of the atom in isolation (atom in ground state);
N=no. of non-bonding valence electrons on this atom in the molecule
B=no. of electrons shared in covalent bonds with other atoms in the molecule.
Formal charge is a test to determine the efficiency of electron distribution of a molecule. This is significant when drawing structures.
Examples:
· Carbon in methane: FC=4 - 0 - (8÷2)=0
· Nitrogen in NO2-: FC=5 - 2 - (6÷2)=0
· double bonded oxygen in NO2-: FC=6 - 4 - (4÷2)=0
· single bonded oxygen in NO2-: FC=6 - 6 - (2÷2)=-1
Calculating Formal Charge Technique:
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For each atom, count the electrons in lone pairs and half the electrons it shares with other atoms.
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Subtract that from the number of valence electrons for that atom: The difference is its formal charge.
Example:
Lewis Structure:
