Question

Why carbon cannot become C⁺⁴ or C⁻⁴?

Answer 1

carbon's electronic configuration can be written as 1s2 2s2 2p2.
see here, carbon needs a lot of energy to lose 2 electrons from its s subshell, which is why c plus 4 cant exist or is very unstable when exists. and, carbon's size is very small which is why c minus 4 is very unstable because the extra electrons will cause e-e repulsion as like charges repel. so, carbon forms covalent bonds i.e it shares its electrons with other elements to form compounds.

Answer 2

C⁺⁴ ion in a compound, a species would have to donate 4 electrons to carbon. The attraction of carbon's nucleus to other atoms' electrons is just too low for that to happen. C ⁻⁴ . anion cannot be formed because 6 protons cannot hold on to 10 electrons. Elements like chlorine form ionic bonds and end up with 18 electrons and 17 protons. The reason that this can happen but carbon cations cannot is that the outermost electrons in a lead atom are much farther from the nucleus than those of a carbon atom and are easier to remove as a result.