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

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