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• professor Dave here, let's talk about the Bohr model of the atom

• once Einstein extendedplanks idea of energy quantization to electromagnetic radiation other

• physicists made some similar strides. Niels Bohr was dealing with some

• problems that were arising with the structure of the atom. if an atom has

• positively charged protons and negatively charged electrons, why are atoms

• stable? why don't the electrons just collide with the nucleus? and what were

• these emission spectra that we can see? what is it about different elements that

• makes them emit light of different colors? bohr answered these questions with

• his model of the hydrogen atom. he extended the idea of energy quantization

• and said that the potential energy of the electron in a hydrogen atom is also

• quantized. this means that an electron can't have any imaginable energy but can

• only inhabit certain energy levels that are at fixed distances from the nucleus

• each type of atom has its energy levels at different values due to its unique

• number of protons in the nucleus and an electron will transition from one energy

• level to another when a photon of a very specific energy is either absorbed or

• emitted by the electron. the energy of the photon will correspond to the difference

• between the two energy levels so if the electron in a hydrogen atom goes from

• the n=3 to the n=2 energy level, a photon will be emitted that is

• equivalent to that specific energy gap. another transition has a different

• energy gap associated with it and therefore generate a photon of that

• particular energy. and to go from lower to higher energy levels an electron

• must absorb a photon of that particular energy. for a hydrogen atom the energy

• levels depend on the Rydberg constant and are given by the following equation

• but we typically just measure the change in energy of an electron during a

• transition so we can modify this equation to include the change in the

• energy level. n final is where the electron ends and n initial is where it

• begins. using this equation we can predict the wavelength of photon

• associated with any

• possible transition for the hydrogen atom. take this transition for example

• from 4 to 2. plug in where the electron starts and where it ends and we get the

• change in energy of the electron which equals the energy of the photon

• from energy we can get frequency

• and from frequency we can get wavelength

• we group the transitions according to the energy level they land on. all the

• ones that end on n=1 are called the lyman series. the ones that end at

• n=2 are the balmer series, and so forth

• notice that the energy level gaps decrease as n increases and n equals

• infinity is actually a finite distance from the nucleus. if an electron goes

• beyond that it is considered to have been ejected from the atom. the Balmer

• series happens to contain transitions that generate photons of visible light

• these are the ones found on the hydrogen emission spectrum. these lines correspond

• to the electrons transitions that end at n=2 and the resulting photon

• that transition emits which just happens to fall in the visible spectrum

• as we said these energies are unique to hydrogen, every element will have its own

• emission spectrum because every element has a unique nucleus and therefore

• differently spaced energy levels. in this way an element's emission spectrum is

• sort of like a fingerprint unique to that element. this is how we can know the

• composition of objects in space, by analyzing the light we see. let's check comprehension

• comprehension thanks for watching guys subscribe to my channel for more

• tutorials and as always feel free to email me

professor Dave here, let's talk about the Bohr model of the atom

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# Bohr Model of the Hydrogen Atom

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Ken Wang posted on 2015/10/14
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