Question

do we find single atoms of H, O, N or C alone, in nature? why or why not.

Answer 1

H, O, and N when alone are found as diatomic molecules H2, O2, and N2. A bunch of single atoms bouncing around in a jar will pair up. If they are not two atom molecules they will be found in compounds such as H2O, NO2. They all need to gain or lose an electron or so to fill their outer shell. Google diamond for example for C which needs four more electrons to fill its outer shell and therefore usually forms multi-atom compounds. https://www.thoughtco.com/chemistry-of-diamond-602110
CO, CO2 ....... everything organic :)

Answer 2

food