After the discovery of the electron and the understanding by Niels Bohr that it exists in energy levels it was proposed in 1923 by French physicist, Louis De Brogile that electrons were not in fact particles but like light could behave as waves. This introduced a two sided behaviour to electrons as both particles and as waves of energy. This stems from Max Planck’s work on quanta. Planck’s theory states that energy can be emitted in quanta, which are small packets of energy and this can be measured by the frequency of light emitted related to the equation E=hv where E is energy, h is plancks constant and v is frequency.
When we examine light we can treat light as a wave as it can be reflected and blocked and is easily visible, however light can also be observed as a particle known as a photon which is a packet of energy (quanta). This was evidenced in the work of the photoelectric effect when light hitting a material causes electrons to be emitted, this is caused by the transfer of energy from light to an electron as kinetic energy.
Niels Bohr was a Danish physicist who made many leaps in theoretical chemistry using mathematical modelling. He developed the model of electrons existing in shells or energy levels.
Max Planck was a German physicist who discovered that energy that is emitted is released in small packets called quanta. He related the amount of energy released to the frequency of the wave.
Quanta is the plural term for quantum which means a small packet of energy. For example a photon is defined as a small packet of energy of light.
Frequency is the number of waves per second. Measured in Hertz, the higher a frequency the more energy emitted
A photo is a particle/wave of energy that is emitted from complexes when an electron that was promoted in energy levels comes back down to the energy level it started in