What are the possible oxidation numbers of carbon?
Actually, the oxidation state of carbon can range from -4 to +4
Carbon is in group 4 (not 14, if you don't want to confuse yourself) - meaning, there are four electrons in its outermost valence shell.
Carbon has an atomic number 6. Thus, if we are to write its electronic configuration:
The outermost shell ( 2s 2p ) has a total of four electrons in this shell (again, just add the superscripts).
The number of electrons in the outermost valence shell will dictate the possible oxidation states of an element.
That is why it is possible for carbon to have an oxidation state of +3.