This paper presents a comparative study was carried out on the physical-chemistry properties based on the ab initio calculations in the HCX (NH2) analogues with 6-311++G (d, p) basis set in gas phase. Natural Bond Orbital (NBO) analysis of these molecules was carried out in order to understand the electronic structures and hybridization of the atoms at the same level of theory. The hyper conjugative interactions and charge delocalization acquired from NBO analysis were used to investigate the stability of compounds. Also, the Natural bond orbital analysis was used to explain the charge transfer or delocalization of charge due to the intramolecular interactions that directly dictates the distribution of electron density. The results showed the stabilization energies related to LpN → σ * C-X (X=O, S, Se) delocalization increase from X=O to X=Se that is in accordance with rise C‌‒‌X bond length in the order C‌‒‌Se > C‌‒‌S > C‌‒‌O. Also, the order of stabilization energies related to LpX → σ * N-C (X=O, S, Se) delocalization represented nucleophilisity property of selenium compounds is higher than sulfur compounds. The values of atomic charge confirmed these results. In this work, resonance weights derived from the Natural Resonance Theory (NRT), are also used to calculate “natural bond order,” پرونده مقاله