Electronegativity:

Definition:

Electronegativity is defined as the relative tendency of atom in a molecule to attract shared pair of electrons to itself.

Explanation:

An American chemist, Linus Pauling, calculated the electronegativities of different elements taking fluorine as a standard. He devised a scale which ranged from O to 4. Fluorine has the highest value of electronegativity of 4.

Group Trends in Electronegativity:

It increases on going across a period from left to right because new shells are being added to each atom and the power of a nucleus to attract electrons decreases.

Periodic Trends in Electronegativity:

It increases on going across a period from left to right because the nuclear charge increases within the same shell holding the electrons tightly.

Electronegativity values help to determine the nature and type of bond. The strength of a bond between two atoms increases with the difference in their electronegativities. If the difference is zero, the bond is non-polar (pure) covalent. If the difference is 1.7, the bond is polar covalent (partially ionic). If the difference is more than 1.7, the bond is ionic.