Identification of mass numbers concerning the nuclei ignite the atmospheric extensive air showers (EAS) is vital in the studies of Ultra High Energetic Cosmic Rays Interactions (UHECRI). The present study introduces a simple technique in processing of the shower data at the detector level (1400 m over sea-level) to identify the nucleus that starts the cascade of the EAS. CORSIKA 7.6900, which is the EAS-Monte Carlo generator is used to generate detailed data at detection level 1400 m over sea-level and energy ~ 10^6GeV. The data are analyzed and the energy spectrum is obtained for the generated EAS. The EAS spectra for light nuclei (H and He), medium nuclei (Mg), and Heavy nuclei (Ti, Cr, Fe) are obtained, totally and with photons are subtracted. It is found that, the spectral slope of the tail of the spectra with photons subtracted depend on the primary nuclei’s mass-number.