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6 CHEMICAL BONDING eLearn.Punjab

It is related to the ionization energy and the electron affinity of the element. Thus, fluorine atom
is more electronegative than hydrogen atom. Pauling calculated the electronegativity values of
elements from the difference between the expected bond energies for their normal covalent bond
and the experimentally determined values.

He devised an electronegativity scale on which fluorine is given an arbitrary standard value 4.0. It
is the most electronegative element. The electronegativity values of other elements are compared
with fluorine, and are given in Table (6.3). Electronegativity has no units.

Animation 6.16: Electronegativity
Source & Credit : makeagif

Variation of Electronegativities in Periodic Table

A comparison of electronegativities shows that the values increase in a period with the
decrease in atomic size. These values decrease in a group as the size of the atoms increase. The
electronegativity differences of the elements can be related to the properties of bonds such as
dipole moments and bond energies.
The difference in the electronegativity values of the bonded atoms is an index to the polar nature
of the covalent bond. When the difference is zero, the bond between the two atoms is non-polar.
Thus, all the bonds which are formed between similar atoms are nonpolar in character, while those
formed between different elements are mostly polar. Elements of widely different electronegativities
form ionic bonds.

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