ABSTRACT
An essential concept for physical chemistry in the twenty-first century is spectroscopy that intertwines developments in astronomy, physics, and technical innovations in instrumentation as now applied to chemistry. While we focus on chemical applications, we can briefly mention historical highlights in physics because the key concept is the quantization of energy. Energy quantization is a revolutionary concept that took most of the early twentieth century to discover, prove, and describe but it is now the backbone of spectroscopy. Spectroscopy measures various forms of light energy that are absorbed or emitted only at specific wavelengths. That is due to the fundamental concept that at the level of atoms and molecules, energy occurs in ‘‘quantum chunks’’ that are so small that in everyday life, we think energy is continuous but it is not. The analogy we offer to students is the difference between smooth peanut butter and chunky style peanut butter, because if you examine smooth peanut butter with a simple lens you can see tiny chunks. Thus, smooth or chunky is a matter of size in peanut butter and also in energy.
