Two lithium nuclei in a lithium vapour at room temperature do not combine to form a carbon nucleus because
a lithium nucleus is more tightly bound than a carbon nucleus
carbon nucleus is an unstable particle
it is not energetically favourable
Coulomb repulsion does not allow the nuclei to come very close
Coulomb repulsion does not allow the nuclei to come very close.
Lithium atom contains 3 protons and 3 neutrons in the nucleus and 3 valence electrons. When two lithium nuclei are brought together, they repel each other. The attractive nuclear forces being short-range are insignificant as compared to the electrostatic repulsion. Thus, the nuclei do not combine to form carbon atom because of coulomb repulsion.