Question

Explain Pauling’s scale of electronegativity.

Answer 1

There is a periodicity in the electronegativity of the atoms along the period and down the group in the periodic table. Pauling studied the behavior and evaluated the result in his Pauling’s scale of electronegativity.

Complete step by step answer:
-Electronegativity is the tendency to attract the shared pair of electrons by an atom. More electronegative the element more is the tendency to find the shared pair of electrons towards that atom.
-Electronegativity generally increases along the period and decreases down the group.
-Pauling found a way to measure the values of electronegativity of atoms and generated his formula for finding the difference between the electronegativity of two different atoms.
-According to Pauling, the electronegativity difference between two atoms can be found with the help of the value of bond energies of the molecules of same as well as of different atoms formed.
-Bond energy is the amount of heat energy needed to break 1 mole of the molecule.
-If one element is A and the other is B, then $\chi A-\chi B|$ gives the value of electronegativity difference between A and B.
-To find this value, we need to find the bond energies of A-A, B-B and A-B.
-We take the geometric mean of bond energies of A-A and B-B and subtract it with the bond energy of A-B and take the root of the value to find the electronegativity difference.

Thus,$$$$ $\chi A-\chi B|$ = 0.1017 $\sqrt{EA-B-\sqrt{EA-AxEB-B}}$
Where
$EA-A$ = bond energy of A-A bond
$EB-B$= bond energy of B-B bond
$EA-B$= bond energy of A- bond
This is the Pauling scale of electronegativity. All the bond energy values must be in kcal/mol.

Note: On Pauling scale, electronegativity of Cl is more than N but practically, electronegativity of N is more than that of Cl. Both have the same value of electronegativity evaluated according to the Pauling scale which is 3.0.
But during solving questions regarding them, we always need to ensure that N will be considered more electronegative than Cl as it is higher in the periodic table. Practically, there is a very slight difference in their electronegativities .