Maheen Zahoor
Friday, 28 February 2014
Electronegativity and Polar Covalent Bonds
Electronegativity:
Definition: The strength of an atom in a bond to attract the electrons towards itself.
The element with a high electronegativity will strongly pull the electrons towards itself than an element with a low
electronegativity.
Bonds:
Bonds
Ionic
Covalent
Polar
Covalent

Non-Polar
Covalent
Ionic Bonds:
o Complete transfer of electrons so the atom gets a complete positive or negative charge depending
on if the atom lost or gained an electron
o Electronegativity difference between the atoms is more than 1.7
o Form crystals which are made up of continuous connection of atom to atom. The units repeat
themselves.
Maheen Zahoor
Friday, 28 February 2014

Covalent Bonds:
o Formation of individual molecules by sharing of electrons
 Non-Polar Covalent Bonds:
o Equal sharing of electrons around the atoms that share those electrons
o Electronegativity difference between the atoms is below 0.4 which means that both the atoms
attract the electrons equally. Therefore, there are no partial charges.
 Polar Covalent Bonds:
o Electronegativity difference between the atoms of the molecule is between 0.4 and 1.7
o The one that has a higher electronegativity among the two atoms attracts the electrons the most in
the molecule. Therefore, the shared electrons spend most of their time around the atom that is more
electronegative. This is unequal sharing because the atom with less electronegativity barely gets the
electrons.
o The “almost” absence of electrons on the less electronegative atom gives it a partial positive charge
and the other atom a partial negative charge. It is partial because there is not a complete gain and
loss.
o The Greek symbol
indicates “partial charge”.
Maheen Zahoor
Friday, 28 February 2014
Bonding Continuum: (The chart behind our periodic tables)
o It is a GUIDELINE to determine if the bond is ionic, non-polar covalent or polar covalent.
0
0.4
Covalent
1.7
Polar Covalent
3.2
Ionic
100%
Covalent
100%
Ionic
Increase in electronegativity.
As the electronegativity increases the bonds go more towards being ionic because we are slowly moving towards a
complete transfer of the electrons. To be completely sure if a substance is covalently bonded or if it is ionic,
experiments need to be performed to gather data that will help us identify the bond.
To understand better, watch this three minute video and learn an hour of stuff in 3 MINUTES WHILE
SINGING! Catchy tune will help you remember.
http://www.youtube.com/watch?v=oNBzyM6TcK8
Homework:
Pg 73 # 1 – 6
Maheen Zahoor
Friday, 28 February 2014
Pg 107 # 1
Pg 108 # 1, 4 – 6
Textbook Reading on Topic:
Pg # 70 – 73, 102 – 108