Atomic spectra

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Atomic spectra

Postby 304634271 » Fri Oct 02, 2015 9:44 am

What is the connection between the atomic spectra (and therefore the spectral lines that correspond to certain energy levels) and the photoelectric effect? I don't really get the sentence "the energy difference is carried away as a photon". Does it mean that for every difference in energy level there is a photon ejected?

Thank you,


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Re: Atomic spectra

Postby VictoriaRoderick_3A » Fri Oct 02, 2015 2:29 pm

I am pretty sure is saying that although a new electron can be emitted, the same one can continue to be emitted, and each time it is emitted it loses more energy.

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Re: Atomic spectra

Postby Chem_Mod » Sat Oct 03, 2015 3:31 pm

The quote "the energy difference is carried away as a photon" is specifically referring to the hydrogen model. The energy of each orbital is given by:

So lets say we have an electron at the first orbital, n=1. In order for the electron to go to n=2, it must somehow gain energy to overcome the gap between n=1 and n=2 which is usually through a photon. This is true for any gap, so every gap has an associated energy difference and that difference usually comes in the form of a photon. These photon energies are discrete, leading to the re-assertion of light as energy packets.

An electron emitted, cannot be re-emitted unless it is somehow captured by surrounding atoms. This does happen in spectroscopy and are called secondary emissions which forms the basis of CCD cameras and photomultipliers. This topic, however, is not being discussed and for all intents and purposes students should consider the emission of an electron as The End for the electron.

The connection towards the photoelectric effect is the reassertion that light behaves as a particle. In both cases, only discrete quantities of light can be absorbed which we call photons. These two fundamentally verifiable experiments is what lead the scientific community to accept the wave-particle duality concept in the 1920's and is as much of a manifest fact as the earth revolving around the sun.

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