Electromagnetic radiation and atomic spectra

Electronic radiation and atomic spectra is the first subtopic in Unit 1 of the Advanced Higher Chemistry course. It contains a deeper investigation of the electromagnetic spectrum in how it occurs, what its uses are and how it relates to individual atoms and substances.

The Electromagnetic Spectrum
This work is largely covered in higher Physics, and is relatively straightforward. The electromagnetic spectrum is the series of electromagnetic radiation; Gamma Rays, X-Rays, UV Light, Visible Light, Infra-red Radiation, Micro Waves and Radio Waves.



All waves in the EM spectum travel at thesame velocity (c = 3x108m s-1) but with different frequencies, energies and wavelengths. Waves with shorter wavelengths (eg gamma rays) have very high frequencies and energies; larger wavelengths make for lower frequencies and energies (eg radio waves).

Wavelength (λ) is the distance of one wave, measured in metres or nanometres or any other compatible measurement (whichever is more suitable).

By the end of this topic, you should know that:


 * there is a spectrum of electromagnetic radiation;
 * electromagnetic radiation can be described in the terms of waves;
 * Electromagnetic radiation can be characterised in terms of wavelength or frequency;
 * the relationship between wavelength and frequency is given by c = f ×LaTeX: $\lambda $;
 * absorption or emission of electromagnetic radiation causes it to behave more like a stream of particles called photons;
 * the energy lost or gained by electrons associated with a single photon is given by E = hf;
 * it is more convenient for chemists to express the energy for one mole of photons as E = Lhf;
 * atomic emission spectra are made up of lines at discrete frequencies;
 * photons of light energy are emitted by atoms when electrons move from a higher energy level to a lower one;
 * each element produces a unique pattern of frequencies of radiation in its emission spectrum;
 * atomic emission spectroscopy and atomic absorption spectroscopy are used to identify and quantify the elements present in a sample.