Electronegativity and Polarity

Electronegativity refers to the attraction an atom has for the shared ppair of electrons in a chemical bond.

As you can see, electronegativity increases as you move diagonally from the bottom left (Francium) to the top right (Fluorine) of the periodic table.

Pauling scale is the most common scale used to measure the atom's electronegativity. It ranges from 0.7 to 4.0, meaning that the electronegativity of Francium is 0.7, whereas the electronegativity of Fluorine is 4.0.


Atoms with higher electronegativity attract its electrons and neighbouring electrons more than those with lower electronegativity. ALSO, stronger attraction means that the electrons in the atoms with higher electronegativity are more difficult to remove. More energy is needed to remove the electrons, so the atoms with higher electronegativity would have higher ionization energy as well.


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From calculating the electronegativity difference between two or more elements involved in the chemical bond, you can find out what type of chemical bond the atoms are most likely to have.

Electronegativity Difference = | Electronegativity1 - Electronegativity2 |

• If electronegativity difference < 0.5, it is a COVALENT BOND
• If electronegativity difference > 1.8, it is an IONIC BOND

But what if 0.5 < electronegativity difference < 1.8 ?

It is called a Polar Covalent Bond and it is the another type of covalent bonding that involves unequal sharing. In this type of chemical bonding, the atom with higher electronegativity pulls the electrons in the bond and electron that are shared towards itself. Polarity is used to describe a molecule's balance, just like density. ( Which atom has more electronegativity and which has less )





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Ex.  Selenium difluoride (SeF2)

Electronegativity difference between Se and F = | 2.55 - 3.98 |
                                                                            = 1.43 ⇒ this is a polar covalent bond

Draw a Lewis Diagram to figure out how many electrons do they share.



In Selenium difluoride, these electrons are shared.



Draw a line to represent a single bond.

In Polar Covalent Bond, atom with higher electronegativity forms a partly negative charge, and atom with lower electonegativity forms a partly negative charge. To show which one has the partly positive and negative charge, δ+ or δ- is marked above each atom.





Also, an arrow is drawn from atom that is δ+ to the atom that is δ- to show that the atom that is δ- is pulling the electrons.