**Applications of electronegativity**

**(1) Nature of bond**

The concept of electronegativity can be used to predict whether the bond between similar or dissimilar atoms is non-polar covalent bond, polar covalent bond (or) ionic bond.

i) When X_{A} = X_{B}, i.e. X_{A} – X_{B} = 0, then A-B bond is non polar covalent bond or simply covalent bond and is represented as A-B. eg. H-H bond in H_{2 }molecule is a covalent bond and is represented as H-H bond.

ii) When X_{A} is slightly greater than X_{B;} (X_{A} – X_{B}) is small, the A-B bond is polar covalent bond and is represented as A^{δ-} – B^{δ+} g. The O-H bonds in H_{2}O molecule are polar covalent bonds and are represented as O^{δ-} – H^{δ+}, since X_{O} > X_{H} and X_{O} – X_{H} is small.

iii) When X_{A} > X_{B}, i.e., X_{A} – X_{B} is very large, A-B bond is more ionic or polar bond and is represented as A^{–} -B^{+}, Since X_{A} >> X_{B}. For example Na-Cl bond in Na Cl molecule is an ionic bond and is represented as Na^{+} Cl^{– }(Here Cl = A and Na = B).

**(2) Percentage of ionic character in a polar covalent bond**

Pauling estimated the percentage of ionic character in various A^{δ-} – B^{δ+} polar covalent bonds from known (XA–XB) values and has derived the following conclusions :

(i) When (X_{A}–X_{B}) = 1.7, the amount of ionic character in A^{δ-} – B^{δ+} bond is 50% and that of covalent character is also 50%. Thus A-B bond is 50% ionic and 50% covalent.

(ii) When (X_{A}–X_{B}) < 1.7, the amount of ionic character in A^{δ-} – B^{δ+} bond is less than 50% and that of covalent character is more than 50%. Thus A^{δ-} – B^{δ+} bond is predominantly covalent and hence is represented as A–B.