Question

Explain the pauling scale for the determination of electronegativity

Answer 1

Electronegativity:-

1. As given by Linus Pauling electronegativity can be described as “the power of an atom in a molecule to attract electrons to itself.”
2. Or we can say that, the electronegativity of an atom is the relative value of that atom's ability to attract electron density toward itself when it bonds to another atom.

Determination of electronegativity using Pauling scale:-

1. The Pauling scale is based on an empirical relation between the energy of a bond and the electronegativities of bonded atoms.
2. Let us consider a bond $A-B$ between two dissimilar atoms $A$ and $B$ of a molecule $AB$.
3. Also let the bond energies of $A-A,B-B,$ and $A-B$ bonds be represented as $E_{A-A},E_{B-B},$ and $E_{A-B}$​ respectively.
4. We may see that the bond dissociation energy of $A-B$ is almost higher than the geometric mean of the bond dissociation energies of $A-A$ and $B-B$ bonds that is, $E_{A-B}>\sqrt{E_{A-A}\times E_{B-B}}$
5. Their difference $(∆)$ is related to the difference in the electronegativities of $A$ and $B$ according to this equation

$$\begin{gathered} ∆=E_{A-B}-\sqrt{E_{A-A}\times E_{B-B}}={(X_A-X_B)}^2 \\ \Rightarrow 0.208\sqrt{∆}=X_A-X_B \end{gathered}$$

6. The factor $0.208$ arises from the conversion of Kcals to electron volt.

7. Here $X_A$ and $X_B$ are the electronegativities of $A$ and $B$ respectively.

8. Considering arbitrarily the electronegativity of hydrogen to be $2.1,$ Pauling calculated the electronegativities of other elements with the help of this equation.

Therefore, with the help of this equation, $$\begin{gathered} ∆=E_{A-B}-\sqrt{E_{A-A}\times E_{B-B}}={(X_A-X_B)}^2 \\ \Rightarrow 0.208\sqrt{∆}=X_A-X_B \end{gathered}$$we can determine electronegativity.