Elucidating atomic emission and molecular absorption spectra using a basic CD spectrometer: a pedagogical approach for secondary-level students

Abstract

Spectroscopy has held a pivotal role in advancing our comprehension of chemistry, dating back to its inception by Robert Bunsen and Gustav Kirchhoff. Nonetheless, access to advanced spectrometers remains restricted, particularly in high schools within developing nations. In this laboratory experiment, students were guided to fashion a spectrometer using reusable materials. This uncomplicated contrivance facilitated the exploration of emission and absorption spectroscopy, acquainting students with atomic spectra marked by electronic transitions, yielding line spectra. Conversely, molecules display not solely electronic transitions, but also vibrational and rotational shifts within chemical bonds, culminating in band spectra. Mobile phone cameras were enlisted as detectors. Captures of sodium and copper atoms emitting light in the course of a flame test, as well as depictions of molecular entities (copper sulphate pentahydrate and potassium permanganate aqueous solutions) absorbing light, were transmuted into the RGB (Red-Green-Blue) color model channels. The learning outcomes exhibited that 86 % of the students successfully discerned between an atomic spectrum and a molecular spectrum. Furthermore, 93 % of the students indicated that the incorporation of mobile devices in fostering scientific comprehension effectively seized their attention, resulting in heightened levels of engagement.