Linus Pauling defined electronegativity as "the power of an atom in a molecule to attract electrons to itself." He developed a method to calculate electronegativity values based on the difference between the measured and theoretical bond energies. The theoretical bond energy is calculated as the square root of the product of the atomic electron affinities. Electronegativity generally increases along periods in the periodic table and decreases down groups, with fluorine being the most electronegative element. Bonds between atoms with similar electronegativity values (<1.7 difference) are predominantly covalent or metallic, while bonds between atoms with larger differences (>1.7) are predominantly ionic.

1. Pauling electronegativity
Dr. Mithil Fal Desai
Shree Mallikarjun and Shri Chetan Manju Desai College
Canacona Goa

2. Linus Pauling described electronegativity
as “the power of an atom in a molecule to
attract electrons to itself.” Linus Pauling
Definition of Electronegativity
e-
e-
Atom A
Atom B

3. Calculating Electronegativity
A B
The factor 0.208 arises from the conversion
electronegativity values from Kcals to electron volt.

4. Calculating Electronegativity
A B
EA-B> EA-A or EB-B
EA-B(measured)> EA-B(theoretical)
Difference in the Bond Energies (Δ)
Δ = EA-B(measured) – EA-B(theoretical)
EA-B(theoretical) = energy for 100% covalent bond
EA-B(theoretical) = (EA-A X EB-B)1/2
Thus
Δ= EA-B(measured) – (EA-A X EB-B)½
δ+ δ-
If X(A) and X(B) are
electronegativity of individual
atoms A and B, respectively,
than
X(A) - X(B) = 0.1017(EA-A X EB-B)½ in kcal mol-1
X(A) - X(B) = 0.208 (EA-A X EB-B)½ in kJ mol-1

5. Periodic trend in Electronegativity

6. Summary
• F is most electronegative element
• If two element have similar(<1.7) electronegativity
values the bond is covalent or metallic.
• If two element have large (>1.7) difference in their
electronegativity values the bond is ionic
predominantly.
As Atomic number increases
• Electronegativity decreases down the group
• Electronegativity increases along the row