What experimental evidence can you cite in support of the hypothesis that the electronegativi-ty of ...

Evidence for this effect can be seen in the observation that the positive end of the di-pole moment in N  C  Cl is on the Cl atom. We conclude that the carbon atom in the cyanide group is more electronegative than a chlorine atom. One can also consider the acidity of ethane, ethene, and acetylene. As the s-character of the hybridization increases (ethane, ethene, acetylene), the pKa decreases ( >50 for ethane, 44 for ethane, and 25 for acetylene). Since pKa is inversely related to electronegativity, it is clear that as the s-character increases, the electronegativity also increases.