Bonding- Helpful Hints
(Chapters 15-16)
Types of Bonds
Ionic bond - A bond generally occurring between metals and nonmetals which
have an electronegativity difference of more than 1.67 – Transfer of electrons
occurs.
Have high melting points.
A very strong bond type. Example:
Na Cl
Non-polar covalent bond – A bond generally occurring between two non-metals
with an electronegativity difference of less than or equal to 0.4 Equal sharing
of electrons occurs.
Have very low melting points.
Example:
H H
Polar covalent bond - Bonds occurring between nonmetals with an
electronegativity difference of greater than 0.4 but less than 1.67 – Unequal
sharing of electrons occurs. Example :
H O
H
Remember that a polar bond is necessary for a polar molecule to exist, but
simply because a polar bond is present does not necessarily mean the
molecule is polar. (example; CO2 is nonpolar because it is a linear molecule)
Metallic bond - “mobile sea of electrons“ . A bond in which delocalized
electrons move between metal atoms, bonding them together. Example:
Double bond – each atom shares 2 pairs of electrons for a total of 4 electrons.
Stronger than a single bond. Example :
O C O
Triple bond - Each atom shares 3 electrons for a total of 6 electrons.
The strongest covalent bond. Example :
N
N
Coordinate covalent bond - A covalent bond in which both electrons are
donated by 1 atom. Common in polyatomic ions. Example :
O
O
S O
O
-2
VSEPR bonding: The concept that the repulsion of electron pairs within a molecule
determines that molecules shape.
# of shared pairs
# of unshared pairs shape of molecule
4
0
tetrahedral
3
1
pyramidal
2
2
bent
1
3
linear
1.
2.
3.
4.
5.
6.
7.

Rules For Drawing Electron Dot Diagrams
For Covalent Molecules
Decide on the central atom:
 Usually it is listed first in the formula
 Usually it is the atom with the lowest Electronegativity
 Hydrogen is never the central atom (it only forms 1 bond)
Arrange the rest of the atoms around the central atom
Count the total number of valence electrons of all atoms
Place one pair of electrons between each bonded atom
Use remaining electrons around the terminal atoms to form stable octets (except H which
needs only two)
If there are any extra electrons, add them to the central atom
If the central atom has fewer that 8 electrons; form multiple bonds (double and triple
bonds
Hints: ▪ If both hydrogen and oxygen are present, bond oxygen to the central atom and
then bond hydrogen to the oxygen.
▪ If more than one carbon atom is present, they will bond to each: C-C-C
van der Waals Forces - Weak forces between molecules (intermolecular forces )
weak, but very important.
London dispersion forces (LDF): Weak bonds that form between nonpolar
molecules due to moving electrons.
Dipole-dipole forces: weak intermolecular bonds that form between polar
molecules
Hydrogen bonds – A type of dipole-dipole force which occurs between a
hydrogen and highly electronegative atoms. Example :
H O
H
H O
H
H O
H
H O
H
Other Vocabulary –
bond dissociation energy
dipole
octet rule
sp3 hybridization