le> Bohr Atomic model
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Bohr Atomic version :In 1913 Bohr suggest his quantized shell version of the atom to explain howelectrons can have steady orbits approximately the nucleus. The activity of theelectrons in the Rutherford version was unstable because, according toclassical mechanics and also electromagnetic theory, any kind of charged particlemoving top top a curved course emits electromagnetic radiation; thus, theelectrons would lose energy and also spiral into the nucleus. Come remedy thestability problem, Bohr modification the Rutherford version by request thatthe electrons move in orbits of fixed size and also energy. The energy of anelectron counts on the dimension of the orbit and is lower for smaller orbits.Radiation can occur only once the electron jumps native one orbit toanother. The atom will certainly be totally stable in the state v the smallestorbit, since there is no orbit that lower energy into which the electron canjump.

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Bohr"s starting point to be to establish that classical mechanics by itselfcould never explain the atom"s stability. A secure atom has actually a certain sizeso that any equation explicate it need to contain some basic constantor mix of constants with a measurement of length. The classicalfundamental constants--namely, the charges and also the masses of the electronand the nucleus--cannot be combined to make a length. Bohr noticed,however, the the quantum constant formulated through the German physicist MaxPlanck has dimensions which, when combined with the mass and also charge of theelectron, develop a measure of length. Numerically, the measure up is closeto the recognized size of atoms. This urged Bohr to use Planck"s constantin in search of a concept of the atom.Planck had introduced his constant in 1900 in a formula explaining thelight radiation emitted indigenous heated bodies. Follow to classic theory,comparable amounts of light power should be developed at every frequencies.This is not only contrary to monitoring but also implies the absurdresult the the full energy radiated by a cook body must be infinite.Planck postulated that power can just be emitted or soaked up in discreteamounts, which he dubbed quanta (the Latin word for "how much"). Theenergy quantum is pertained to the frequency of the irradiate by a newfundamental constant, h. When a human body is heated, that radiant energy in aparticular frequency variety is, according to classical theory, proportionalto the temperature of the body. With Planck"s hypothesis, however, theradiation can occur only in quantum amounts of energy. If the radiantenergy is less than the quantum that energy, the amount of irradiate in thatfrequency selection will it is in reduced. Planck"s formula correctly describesradiation indigenous heated bodies. Planck"s continuous has the size ofaction, which may be to express as systems of energy multiplied by time,units of inert multiplied by length, or devices of angular momentum. Forexample, Planck"s continuous can be created as h = 6.6x10-34 jouleseconds.Using Planck"s constant, Bohr obtained an accurate formula because that the energylevels of the hydrogen atom. The postulated the the angular momentum ofthe electron is quantized--i.e., it can have just discrete values. Heassumed the otherwise electrons obey the laws of timeless mechanics bytraveling roughly the cell core in one orbits. Since of thequantization, the electron orbits have fixed sizes and also energies. Theorbits space labeled by an integer, the quantum number n.
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With his model, Bohr described how electrons could jump native one orbit toanother just by emitting or taking in energy in addressed quanta. Because that example,if an electron jumps one orbit closer to the nucleus, it need to emit energyequal come the distinction of the energies the the two orbits. Conversely,when the electron jumps come a larger orbit, it must absorb a quantum oflight same in energy to the difference in orbits.

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Excerpt indigenous the Encyclopedia Britannica without permission.