Metakaolin-based geopolymers were synthesized using two different activator solutions, sodium silicate (Na2SiO3) and phosphoric acid solution (H3PO4). A comparative study of the characteristics of alkaline and acidic geopolymers was performed using FTIR, Raman and quantum chemical calculation of the oligomeric structure of geopolymer matrices with a focus on the comparison of the spectrometric data obtained from synthesized geopolymer samples. The mechanical stability of the obtained geopolymer materials was also examined. After a 14-day period of nurturing the results obtained show that the compressive strength of geopolymer mortar based on sodium silicate is greater (30,2 MPa) than that obtained in an acidic medium (9,4 MPa). Geopolymer pastes have lower compressive strength due to lack of filler. Phosphate geopolymer systems have shown a certain limitation in their synthesis The phosphate paste was extremely brittle, while phosphate mortar requires a high purity aggregate due to phosphoric acid and aggregate reactions (gas formation causes higher porosity). The paper showed excellent agreement between the quantum chemical model and experimental data (FTIR and Raman), which indicates the success of geopolymer synthesis in alkaline and acidic systems. FTIR has proven to be an excellent characterization technique for metakaolin-based geopolymer systems. Raman proved to be an inappropriate structural characterization method due to the presence of high crystallinity anatase in the metakaolin system and due to the occurrence of fluorescence.