Based on the results collected, we researched on why some chemicals gave out the same colour when burnt. Visible spectroscopy is the study of the interaction of radiation from the visible part (λ = 380 -
720 nm) of the electromagnetic spectrum with a chemical species. Light travels in packets
of energy called photons. Each photon has a specific energy related to a certain frequency or
wavelength by using the formula (E = hν = hc/λ). Visible light consists of wavelengths ranging from 380 nm (blue violet) to 720 nm (red). When all wavelengths of visible light are present, the light appears "white" to our eyes. If any wavelength is removed (absorbed), we perceive the remaining
combination of wavelengths of light as the "complimentary" color (Table 1, Figure 1).
For example, if white light passes through a test tube containing a solution of copper (II) sulfate (CuSO4), the solution will be blue because the Cu2+ ions strongly absorb “orange” photons of light (photons of light with λ ~ 600 nm). When a photon of colored light is absorbed by a compound an electron transitions from lower energy orbital to higher energy orbital. The energy of absorbed radiation is equal to the energy difference between the highest energy electronic occupied orbital (OO) and the closest unoccupied orbital (UO). Many transition metal complexes and large conjugated organic
molecules are brightly colored because this energy difference is equal to an energy within the
visible region of the electromagnetic spectrum.
After further research, we also found out that before absorbing energy, the electrons are in the lowest energy orbitals possible, which is in the ground state. When energy is absorbed, the electron in the compound is promoted from an occupied orbital to an unoccupied orbital, which is the excited stage. The required amount of energy or light required for each chemical differs. Once in solution, the amount of a particular energy of light passing (transmitted) through that solution is quantified as transmittance. Transmittance is calculated by taking the ratio of the intensity (amount) of light leaving the chemical sample (I) to the intensity (amount) of light entering the chemical sample (Io). (Figure 3)
Upon evaluation of our hypothesis and our research, we can conclude that our hypothesis is proven. This is because research and experimentation have proved that chemicals that electrons require the same amount of energy to reach an orbital stage will absorb the same colour and give out the same colour.
Visible Spectroscopy. (n.d.). Retrieved August 15, 2013, from https://eee.uci.edu/programs/gchem/RDGVISSpec.pdf