NOTES: TYPES OF CHEMICAL BONDS
Name___________________________________
Date_________________Block______________
What is a chemical bond?

A strong attractive force between atoms in a compound

Ionic: attraction of __________________ ______________ ___________

Covalent: attraction of the nucleus of each atom to a ________ pair of valence electrons

Metallic: attraction of _________________charged metal ions to the mobile valence
electrons in the metal
The Octet Rule

The Octet Rule:

Atoms will lose, gain, or share valence electrons until each atom achieves…
an _________of valence electrons
a total of _____valence electrons
a __________ _________ electron configuration

The Octet Rule is our guiding principle in the formation of chemical bonds between atoms
Types of Bonds

Ionic: atoms lose or gain valence electrons, forming + and – ions, which are then
attracted to one another because they are ____________ charged

Covalent: atoms ___________ valence electrons, the nuclei of both atoms are strongly
attracted to the shared valence electrons, forming the bond
May be nonpolar (equal sharing) or polar (__________sharing)

Metallic: the valence electrons of atoms in the metal are mobile, leaving the metal
atoms with a ___ charge, the + charged metal ions are attracted to the free-floating
___________
What determines the type of bond formed between two atoms?

The “_________ _________ ________” for electrons!

Atoms play “tug of war” with electrons

The _____________________ of the atoms determines their “strength” in the tug of war

Electronegativity is a measure of the tendency of an atom to _________ a bonding pair
of electrons.

The Pauling scale is the most commonly used. Fluorine (the most electronegative
element) is assigned a value of ________ and values range down from there
NOTES: TYPES OF CHEMICAL BONDS
Name___________________________________
Date_________________Block______________
Consider two atoms…

Atom A and Atom B form a bond…
What if atom B is a lot more electronegative than atom A?

Sometimes one of the atoms is much stronger (more electronegative) than the other, and
“wins” the electron- this results in a transfer of electron(s) to form ions, and thus an _____ ____

Consider a bond between two atoms, A and B.

In this case, the electron pair is dragged right over to B's end of the bond. A has lost
control of its electron, and B has complete control over both electrons. Ions have been
formed.
A+1 --------:B-1
What happens if B is slightly more electronegative than A?

Sometimes one of the atoms is a little stronger than the other, but not strong enough to “win”
the electron

This results in ____________sharing of electrons, which is a polar covalent bond

B will attract the electron pair more than A does.

That means that the B end of the bond has more than its fair share of electron density and so
becomes __________ ____________. At the same time, the A end (rather short of electrons)
becomes slightly positive.
δ+
A--------:---Bδ-
(note that δ is pronounced “delta” means “_________”, so δ+ means slightly positive and δ- means
slightly negative. The δ- will always be on the more electronegative of the two atoms)

This is described as a polar bond (or polar covalent)- a covalent bond in which there is a
________________ of charge between one end and the other

in other words one end is slightly positive and the other __________ ___________.

The electron density lies __________ to one atom than the other

Examples include most covalent bonds. The hydrogen-chlorine bond in HCl or the
hydrogen-oxygen bonds in water are typical
NOTES: TYPES OF CHEMICAL BONDS
Name___________________________________
Date_________________Block______________
What happens if two atoms of equal electronegativity bond together?

Sometimes the atoms are equal or nearly equal in their strength (electronegativity), and neither
wins

This results in ___________sharing of the electron(s), and thus a nonpolar covalent bond

If the atoms are equally electronegative, both have the same tendency to attract the bonding
pair of electrons, and so it will be found on average _________ ______ between the two atoms.
A-----:-----B

To get a bond like this, A and B would usually have to be the ______atom. You will find this sort
of bond in, for example, H2 or Cl2 molecules.
How to determine bond type

The ________________ in electronegativity between the two atoms is what determines
whether a bond is ionic, polar covalent, or nonpolar covalent

To determine the bond type
Look up the electronegativity values for the two atoms in the bond

__________to find the difference
Use the chart (next slides) to determine the type of bond

Difference in electronegativity
Type of Bond
0- 0.3
covalent
____________
0.4- 1.0
moderately
polar covalent
1.1- 1.7
very polar
covalent
> 1.7
__________
% Ionic Character

Bonds can also be described based on their % ionic character, which is another way to express
the degree of polarity in the bond.

100% ionic character would represent a purely __________bond

0% ionic character would represent a purely __________ bond
NOTES: TYPES OF CHEMICAL BONDS
Name___________________________________
Date_________________Block______________
Let’s compare ionic and covalent
IONIC:
•
Transfer of electrons to form ions due to __________ electronegativity difference between the
two atoms
•
Oppositely charged __________ are attracted
•
The ions build up in a 3 dimensional crystal lattice; there are not individual __________
•
The chemical formula represents a __________ __________: the lowest whole number ratio of
ions that is neutral
POLAR COVALENT:
__________ sharing of electrons due to some electronegativity difference between the two atoms
•
Electron clouds ____________and electrons are shared unequally to form bond
•
Individual molecules are formed
•
The chemical formula represents a __________________
NONPOLAR COVALENT:
•
Equal sharing of electrons since the two atoms have __________ or nearly equal
electronegativities
•
Electron clouds __________ and electrons are shared equally to form the bond
•
Individual molecules are formed
•
The chemical formula represents a ____________