Quantum comes from the Latin: quantum = How Much. The history of quantum mechanics began essentially with the 1838 discovery of cathode rays by Michael Faraday, the 1859 statement of the black body radiation problem by Gustav Kirchhoff, the 1877 suggestion by Ludwig Boltzmann that the energy states of a physical system could be discrete, and the 1900 quantum hypothesis by Max Planck that any energy is radiated and absorbed in quantities divisible by discrete ‘energy elements’ ε such that each of these energy elements is proportional to the frequency ν with which they each individually radiate energy..... Wiki: http://en.wikipedia.org/wiki/Quantum_mechanics The discovery of the neutron (1932) by Chadwick opened the field of Atomic Chemistry. Quantum ideas advanced greatly as methods of observation went from Picometres into the Femtometre range.