[TechOutsider]

Which of the following increase(s) for the bonding between carbon atoms in the sequence
of molecules C2H6, C2H4 and C2H2?

I. Number of bonds II. Length of bonds III. Strength of bonding

Would it be both III because double bonds are stronger than single bonds; carbon *must* form 4 bonds so it doubles up on bonds with the hydrogen?

But the answer is I and III. I don't understand there would be more bonds.

[rabolisk]

The number of bonds between the carbons increases as you go from single to double to triple, just as the names would suggest.