A new heuristic model for the calculation of the formation energy of the carbon nanoclusters was proposed. The model uses only three parameters: two energies, E c and E 5 , are determined from the comparison with the experimental data, the results of computer simulations for various carbon nanoclusters, and the last one is the dangling carbon bond energy, E b . The knowledge of the energies of the formation of the carbon cluster series, obtained in the frame of the unified phenomenological approach, allows one to judge the relative energetic stability of these clusters. The dangling bond passivation is shown to change drastically the phase diagram of the co-existence of the clusters of the different type.