Covalent Bond Notes
In a covalent bond:
1. The electronegativity differences in the 2 atoms involved is not extreme, so the electrons that are
interacting are shared (less than 2.1 difference)
2. It may not be an equal sharing, but at least the electrons are being shared.
3. When a covalent bond forms with unequally shared electrons, the bond is said to be a polar
covalent bond. (between 2.1 & .4 electronegativity difference)
a. The uneven sharing causes the more electronegative atom to have a partial negative charge.
b. The other atom will have a partial positive charge.
Polar Covalent!
1. If the whole molecule has a tendency to develop a positive end and a negative end to it, because of
differences in electronegativity it is called a polar molecule
2. These oppositely charged “poles” set up by the electronegativity differences in atoms causes
interaction between molecules.
3. The partial negative charges of one molecule attracts the positive
end of another molecule and so on setting up a network of loose
connections
4. These connections lead to different chemical properties; such as
higher boiling points because it takes more energy to pull the
molecules apart
The Glue That Binds!
The balance set up by repulsion and attraction between two atoms in a covalent bond, is what holds
the atoms together
Lewis Structures:
Using Lewis structures we can begin to predict the results of sharing valence electrons to achieve the
same configuration as the nearest noble gas.
For instance how many bonds do you predict the following nonmetals will make?
Octet Rule
To be stable the two atoms that are involved in the bond share their electrons in order to have 8 valence
electrons. Atoms with 8 valence electrons are more stable because they are at a lower state of energy.
Lewis Structures:
The Lewis structures that you have seen so far use a pair of dots to represent covalent bonds.We can also
use dashes to represent a pair of bonding electrons. There are three types of bonds, single, double, and
triple – depending on how many electron pairs are shared.
Six steps to Writing Lewis Dot Structures:
1)Count the total valence electrons for the molecule (valence electrons for each atom and add them up)
2)Figure out how many octet electrons the molecule should have, using octet rule (everyone wants 8
except hydrogen, which is happy with
3)Subtract the valence electrons from the octet electrons (these are the number of electrons involved in
bonding)
4)Divide the number from 3 by two (these are the number of dashes or bonds in the molecule)
5)Draw an arrangement of the atoms for the molecule that contains the # of bonds you found in #4.
 Hydrogen and the halogens only form 1 bond
 Oxygen family forms 2 bonds
 Nitrogen family forms 3 bonds
 Carbon family forms 4 bonds and is usually the central atom
 Hint: bond all the atoms together by single bonds, and then add the multiple bonds until the rules
above are followed
6)Find the number of lone pair (nonbonding) electrons by subtracting the bonding electrons (#3 above)
from the valence electrons (#1 above). Arrange these around the atoms until they satisfy the octet rule.
Lewis structures can be drawn for the polyatomic ions too… The only difference is you must alter
the # of electrons to reflect the total charge of the polyatomic ion.
Naming Covalent Compounds:
 Naming molecular or covalent compounds is fairly easy. It’s similar to naming binary ionic
compounds, except covalent compounds use prefixes
Prefixes to use:
• Mono- (1)
• Penta- (5)
• Nona- (9)
• Di- (2)
•Hexa- (6)
•Deca-(10)
• Tri- (3)
• Hepta- (7)
• Tetra- (4)
• Octa- (8)
A prefix is added to an element to tell how many of that element are in the compound
We will work with binary compounds almost exclusively when naming covalent compounds
Rule #1 Name the first nonmetal with the proper prefix (if there is only one of the 1st element, you do
not use the prefix mono).
Rule #2 Name the second nonmetal with the proper prefix and change the ending to –ide.