Question

two carbon atoms can't be linked each other by more than three convalent bonds why?​

Answer 1

Answer:

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since,there is a single bond between the two carbon atoms and both share their one atom therefore for completing its shell it need to combine with three atoms of carbon or other element . therefore it cannot be linked to more than 3 covalent bonds since its shell will be completed to become stable .

Answer 2

The strength of a covalent bond depends on whether it is a single, double or a triple bond. But why is that? As the number of bonds increases, the bond length decreases. So, triple bonded carbons are closer to each other than double bonded carbons. As you know, attractive forces increase exponentially with decrease in separation.

However, there is a limit. Because even repulsive forces have a say in this.

As the atoms get closer, the electron-electron repulsions start to become significant, and the energy of the system(two carbon atoms) begins to increase.

As the energy increases, the system becomes unstable.

It just so happens that triple bond is the closest you can go without decreasing the stability of the two bonded carbons.