I have researched each compound.
NH3 is stable.
CH is unstable The Carbon atom wants 3 more electrons in its 2nd shell.
CO2 is stable.
CH2 is unstable. The Carbon atom wants 2 more electrons in its 2nd shell.
N is unstable. It needs 3 more electrons in its 2nd shell.
NH is unstable. It needs 2 more electron in its 2nd shell.
So how does it all fit together?