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The $CO$ triple bond has a bond enthalpy of 1072 kJ/mol while the $N_2$ triple bond has a bond enthalpy of 945 kJ/mol, at least according to my source. The molecules are isoelectronic, so I couldn't think of any way to explain it using MO theory. I've read many explanations that did not make much sense, including

Of course because they are different elements and nitrogen nitrogen bond is balanced and oxygen is more electronegative than nitrogen so it will have a greater bond strength

So my question is why is the $CO$ triple bond stronger than the $N_2$ triple bond?

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    $\begingroup$ I don't exactly see what answer would you want. The two molecules are different, so one has to have stronger bond. This rationalisation you mention indeed doesn't make much sense. Unless you want to get into serious computational chemistry, there probably isn't much to talk. $\endgroup$ – Mithoron Mar 20 at 23:03
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    $\begingroup$ Somewhat related chemistry.stackexchange.com/questions/66919/… chemistry.stackexchange.com/questions/30797/… $\endgroup$ – Mithoron Mar 20 at 23:05
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    $\begingroup$ To add to Mithoron's point, one molecule is heteronuclear, and one is homonuclear. So at a high level, you're comparing apples and oranges. $\endgroup$ – MaxW Mar 20 at 23:44
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I agree in part with Mithoron and MaxW's comments: these are different molecules, not even sharing a mutual atom (e.g. C-O vs C-C), so direct comparison is restricted.

However, Pauling's concept of electronegativity does explain why, in general, the heteronuclear A-B bond is stronger than the average of the homonuclear A-A and B-B bonds. the difference in the electronegativity of the two atoms in the bond lend a somewhat ionic character to the bond, strengthening it.

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