Electronegativity And Its Effect On Bond Type

The summary at your level is that:

1.       No electronegativity difference between two atoms results in a non polar covalent bond.

2.       Slight electronegativity difference between two atoms results in a polar covalent bond.

3.       Large electronegativity difference between two atoms results in an ionic bond.

In general, situation 1 above involves two identical non metal atoms, situation 2 involves two non identical non metals and situation 3 involves a metal and a non metal.

References differ in regard to what bond types are denoted by electronegativity differences:

Reference 1 electronegativity difference ranges:

EN = 0.0                                -              Non polar covalent

0.0 < EN < 2.0                      -              Polar covalent

EN > 2.0                                -              Ionic

Reference 2 electronegativity difference ranges:

0.0 < EN < 0.6                     -              Non polar covalent

0.6 < EN < 1.8                     -              Polar covalent

EN > 1.8                               -              Ionic

Reference 2 is more in line with what you will have to know at this point.

So the question that will arise, is do you have to learn electronegativity values for CSEC exams. The answer is no. It will be sufficient to know that:

1.       The most electronegative elements are non metals on the top right hand side of the periodic table.

2.       The least electronegative elements are metals on the bottom left hand side of the periodic table.

3.       Electronegativity increases from left to right across a period.

4.       Electronegativity increases as you ascend a group.

These are, of course general rules. Exceptions will be met at CAPE (See group 4).