Covalent Bond
Discusses the sharing of electrons, Lewis structures, formal charge, and limitations of the octet rule.
What is Covalent Bond?
A chemical bond formed by the sharing of one or more pairs of electrons between atoms.
Key formula / rule: Formal Charge
Key points
- Define covalent bonding and explain its origin.
- Differentiate between single, double, and triple covalent bonds.
- Draw Lewis structures for simple molecules.
- Calculate formal charge on atoms in a Lewis structure.
Common exam trap
Confusing covalent bonding with ionic bonding (transfer vs. sharing of electrons).
Definitions
- Term
Covalent Bond
- Meaning
A chemical bond formed by the sharing of one or more pairs of electrons between atoms.
- Term
Lewis Structure
- Meaning
A diagram that shows the bonding between atoms of a molecule and the lone pairs of electrons that may exist in the molecule.
- Term
Octet Rule
- Meaning
A rule stating that atoms tend to combine in such a way that they each have eight electrons in their valence shell, giving them the same electronic configuration as a noble gas.
- Term
Formal Charge
- Meaning
The hypothetical charge assigned to an atom in a molecule, assuming that all bonds are purely covalent and that electrons in a bond are shared equally.
- Term
Polar Covalent Bond
- Meaning
A covalent bond in which the sharing of electrons is unequal, due to a difference in electronegativity between the bonded atoms.
Learning objectives
Define covalent bonding and explain its origin.
Differentiate between single, double, and triple covalent bonds.
Draw Lewis structures for simple molecules.
Calculate formal charge on atoms in a Lewis structure.
Explain the octet rule and its exceptions.
Relate covalent bonding to molecular stability.
Formulae
- Name
Formal Charge
- Note
V = Valence electrons of the free atom, N = Non-bonding electrons (lone pair electrons), B = Bonding electrons (shared electrons in bonds).
- Expression
FC = V - N - 1/2 B
Prerequisites
Atomic structure (protons, neutrons, electrons).
Electron configuration.
Valence electrons.
Electronegativity.
Common mistakes
Confusing covalent bonding with ionic bonding (transfer vs. sharing of electrons).
Incorrectly drawing Lewis structures, leading to wrong electron counts.
Assuming all atoms strictly follow the octet rule.
Miscalculating formal charges.
Not considering electronegativity differences for bond polarity.
Keywords
Covalent bond
Electron sharing
Lewis structure
Octet rule
Formal charge
Valence electrons
Molecule
Non-metal
Bond order
Electronegativity
Practice preview
Which of the following statements about covalent bonds is INCORRECT?…
easy
What is the primary reason for the formation of a covalent bond?…
easy
In the Lewis structure of water (H₂O), how many lone pairs of electrons are present on the oxygen atom?…
easy