COVALENT BONDING
A. Concepts
1. The bonding electrons will move about both nuclei, effectively filling both orbits.
2. molecule- a neutral group of atoms held together by covalent bonds.
3. diatomic molecule- a molecule containing only two atoms.
4. Non-noble gases occur as covalent, diatomic molecules- H2, N2, O2, F2, Cl2, additionally,
Br2 and I2 exist as diatomic molecules.
5. molecular compound- a chemical compound whose simplest units are molecules.
6. chemical formula- notation showing the number of atoms of each kind of element in a
compound by using symbols and subscripts.
7. molecular formula- a chemical formula showing a single molecule of a molecular compound.
B. Bonding Process
1. octet rule- the formation of compound occurs so that each atom ends up with an octet of
electrons in its highest energy level.
2. bond length- the average distance between two bonded atoms; occurs at the minimum
potential energy.
3. bond energy- the energy needed to break a chemical bond and form neutral isolated atoms.
4. Sharing of electrons can involve one pair (single bond), two pairs (double bond) or three
pairs (triple bond) of electrons.
5. polyatomic ions- group of covalently bonded atoms that remains charged.
C. Notations
1. electron dot (Lewis) notation- valence electrons are shown, indicated by dots around the
element symbol.
Ex. Electrons are placed around the symbol in a counterclockwise fashion.
3rd
6th
2nd
7th
Symbol
8th
1st
5th
4th
(see diagram #1)
2. Lewis structures- formulas in which symbols represent the kernel of an atom and dot pairs or
dashes represent electron pairs in covalent bonds, while dots adjacent to one symbol
represent unshared electrons.
(see diagram #2)
3. structural formula- drawing that indicates the bonds present, but not the unshared pairs of
electrons in a molecule.
(see diagram #3)
4. resonance structure- notation that shows more than one structure because the molecules or
ions cannot be represented by one structure.
(see diagram #4)
Diagram #1 Electron Dot Notations
Diagram #2 Lewis Structures
Diagram #3 Structural Formulas
Molecular Formula
Electron Dot Diagram
H
··
H : C : H
··
H
Structural Formula
H
|
H - C - H
|
H
Molecular Formula
Electron Dot Diagram
Structural Formula
HCN
H : C ::: N :
H - C  N
Molecular Formula
Electron Dot Diagram
Structural Formula
C2H6O
H
H
·· ·· ··
H : C : C : O : H
·· ·· ··
H
H
H
H
|
|
H - C - C - O - H
|
|
H
H
Electron Dot Diagram
H
H
·· ·· ··
H : C : O : C : H
·· ·· ··
H
H
Structural Formula
H
H
|
|
H - C - O - C - H
|
|
H
H
CH4
Molecular Formula
C2H6O
Diagram #4 Resonance Structure
The correct way to describe ozone as a Lewis structure would be:
This indicates that the ozone molecule is described by an average of the two Lewis structures.