Then the n=3 orbit can fit three wavelengths, etcĭe Broglie replaced Bohr's stable "orbits" with "standing wave modes".Įvidence of the wave behaviour of electrons was found in 1927 by American physicists Davisson and Germer who observed electron diffraction, diffraction being a property of waves. The next orbit, n=2, corresponds to an orbit two wavelengths long. 2Ĭlose to the nucleus, n=1 of the Bohr model, the energy of the electron provides for an orbit corresponding to 1 wavelength. You can have 1 wavelength or 2 wavelengths, but you can't have ½ a wavelength nor can you have 1.75 wavelengths. Louis de Broglie realised that if an electron is confined to an orbit around the nucleus, standing waves would be set up, that is, the orbit of an electron would correspond to a fixed whole number of wavelengths for the electron.įractions of wavelengths are not allowed. If electrons can be considered as a wave, then an electron close to the nucleus would have a longer wavelength than an electron further from the nucleus. In the Bohr model of the atom, an electron close to the nucleus has less energy (lower speed) than an electron further from the nucleus (faster moving electron). Increasing the speed of a particle reduces its wavelength (and thereby increases its frequency) Increasing the mass of a particle reduces its wavelength. He said that the wavelength (λ) of a particle should be inversely proportional to both the : In 1924, French physicist Louis de Broglie suggested that particles might also have a wave-particle dualism and sometimes act as waves. This is referred to as the wave-particle dualism of radiation. In 1905, Albert Einstein showed that light could be considered as both a wave and a particle. It did not answer the question of why electrons should move in circular orbits at fixed distances from the nucleus. This model was designed to explain the hydrogen emission spectrum, which it did quite well, but it was an uncomfortable mix of classical physics and the quantisation of energy. Orbits close to the nucleus were of less energy than orbits further away from the nucleus. The Bohr model for the atom, proposed by Niels Bohr in 1913, had negatively charged particles called electrons orbiting around the positively charged nucleus in fixed circular orbits as shown on the right, much like the planets orbit the sun.
No ads = no money for us = no free stuff for you! de Broglie (b) Energy sub-levels (subshells) contain a number of orbitals. (a) Energy levels (shells) contain energy sub-levels (subshells). The term "orbital" refers to the shape of the volume of space in which there is the greatest probability density.This "distribution" of probability is referred to as "probability density".Ĭhemists often use the term "charge cloud" instead of probability density.The probability of finding an electron within a volume of space is dependent on the distance from the nucleus, there are volumes in which it is highly likely an electron will be found, and volumes in which it is very unlikely an electron will be found.