<p>For a diatomic molecule AB, the electronegativity difference between A and B = 0.2028<math xmlns="http://www.w3.org/1998/Math/MathML"><msqrt><mo>&#8710;</mo></msqrt><mo>&#160;</mo><mo>[</mo><mo>&#160;</mo><mi>w</mi><mi>h</mi><mi>e</mi><mi>r</mi><mi>e</mi><mo>&#160;</mo><mo>&#8710;</mo></math>&nbsp;= Bond energy of AB - Geometric meean of the bond energies of&nbsp;&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>A</mi><mn>2</mn></msub><mo>&#160;</mo><mi>a</mi><mi>n</mi><mi>d</mi><mo>&#160;</mo><msub><mi>B</mi><mn>2</mn></msub><mo>]</mo></math>. The electronegativities of fluorine and chlorine are 4.0 and 3.0 respectively and the bond energies are of F-F : 38 kcal&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>&nbsp;and Cl-Cl: 58 kcal&nbsp;<math xmlns="http://www.w3.org/1998/Math/MathML"><mi>m</mi><mi>o</mi><msup><mi>l</mi><mrow><mo>-</mo><mn>1</mn></mrow></msup></math>. The bond energy of Cl-F is:</p>