What's the difference between Carbon bonding and Carbonide bonding?
Carbon is a tetravalent element; it has 4 electrons available to form covalent bonds. Carbon can have the oxidation state of +4/-4 among other uncommon oxidation states. However, C2 -2 is an ion( acetylide) that results from the removal of two protons from acetylene C2H2. Acetylide can strongly bond to a metal cation to make an ionic compound such as K2C2 with the structure K+ -C≡C- K+.
Hydrogen is unlike any other element, it has only one electron, so there is not much electron shielding around the nucleus of the atom. Hydrogen is more electronegative than K, so it can bond more readily with most elements.
C2N2 contains covalent bonds between two carbons and two nitrogens, it has the structure N≡C-C≡N. It does not have the ion C2 -2 that looks like this -C≡C-
I hope this helps!