Chemical Bonding!

3 Types of Bonding:
1) Ionic bonding- the transfer between 2 atoms to form a positive ion and negative ion.
2) Non-polar covalent bonding- equal sharing of electrons
3) Polar covalent bonding- unequal sharing of electrons

So let's start with ionic bonding. This uses the electrostatic force. This is the force that exists between charged particles as a result of attraction/repulsion. It operates equally in all directions. It's important to know that ionic bonds are very strong, so compounds held together with this bond have a high melting temperature.  

We know that in an ionic bond, a metal and non metal combines. Why does the metal lose valence electrons? This is explained by electronegativity. Metals have a low electronegativity and non metals have high electronegativity which results in high ionization energies. The difference in this electronegativity will determine the electron sharing. The Pauling Scale (picture) measures electronegativity.  To find the electronegativity difference, you can use this formula: 

ENeg Diff. = lENeg1 - ENeg 2l

If ENeg Diff <0.5 it's a non polar covalent bond

If ENeg Diff > 0.5 and <1.8 it's a polar covalent bond

If ENeg Diff > 1.8 it's an ionic bond

Now about non polar covalent bonding. It involves equal sharing to satisfy the octet rule. It is VERY STRONG. Now for some of these bonds such as CH4, O2, and F2, they have low melting points. Why? Because of weak bonds.  
So what holds the bonds together? Intramolecular forces that are found within the molecule, and responsible to hold the atoms of molecules together. Intermolecular forces are between molecules and are responsible for the bonding between molecules. 
London Forces are weak attractive forces due to temporary dipolar attractions between neighbouring atoms. They can exist individually or parts of a molecule. Also the greater the atomic number of the atom, the stronger the London force occurs. What's a dipole? It's a partial separation of charge where one end of a molecule/bond has a slight excess positive charge and the other end has a slight excess of negative charge. 

The last bonding is polarity which involves the molecule's electrical balance. If there's an imbalance, it's polar. If it's balanced, then it's non polar. 
Electronegativity effects this because the greater of this it has, the greater pull of the electrons in the bond will be pulled more towards itself and the shared electrons spend more time near the atom. High electronegativity results in partial negative. (δ- between 0 & -1) Low electronegativity results in partial positive. (δ+ between 0 & +1) The δ symbol represents partial. 
An arrow indicates the migration of electrons. It will point to the partial negative atom involved in the bond. An example is H2O:

 H: 2.20
 O:3.44


3.44-2.20= 1.24
This means it is a polar covalent bond.

 

A quiz to practice. =)