Why does not carbon form C+4 or C-4 ions? Explaine.

To form C4+ions , four electrons are to be removed from carbon, which require a high value of ionization  energy. It is not available under ordinary conditions. 

To form C4-, four electrons are to be added to carbon, which require a very high energy to overcome repulsions between C- and the electrons being added. That why carbon does not form C+4 and C-4 ions.

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