SPECTROSCOPY :D

[peepala]

SOMEONE PLEASE EXPLAIN HOW SPECTROSCOPY WORKS, ESPECIALLY IN TERMS OF ELECTRON ENERGY LEVELS AND WHY DIFFERENT ELEMENTS EMIT DIFFERENT FREQUENCIES OF LIGHT?

THANKYOU 

[spectroscopy]

you summoned me?

[keltingmeith]

Tbh, I'd love to answer your question, but the all caps is giving me such an eye-sore that I don't know what you're asking...

[Mieow]

WHY ARE YOU YELLING AT ME?!?! OR ARE YOU JUST REALLY EXCITED ABOUT CHEM?

Anyway, try reading up about it here http://www.chemguide.co.uk/analysis/uvvisiblemenu.html#top
Quite comprehensive, but be aware that there is definitely some info that is not on the study design and thus you won't need to know(referring to the study design to see what you need to know would be advisable). Alternatively you could watch the video of spectoscopy on vTextbook which can be found under 'Resources' at the top of the page

[Kel9901]

SOMEONE PLEASE EXPLAIN HOW SPECTROSCOPY WORKS, ESPECIALLY IN TERMS OF ELECTRON ENERGY LEVELS AND WHY DIFFERENT ELEMENTS EMIT DIFFERENT FREQUENCIES OF LIGHT?

THANKYOU 

>caps but ok i'll try

Electrons become excited when they move up an energy level, and become de-excited (is this a word) when they move down to the ground state (lowest energy level). An atom's electrons have multpile discrete energy levels which you'll learn about in unit 4 of physics if you're doing that (you don't need a ton of knowledge about it in chem, only a limited bit). Electrons in higher energy levels have greater potential energy which may be released  in the form of electromagnetic radiation (light)

In flame tests/atomic emission spectroscopy, the flame gives energy to the electrons allowing them to move up energy levels. As they fall back down, they release the energy in the form of light, and this light is what is analyzed. This is qualitative analysis only

In atomic absorption spectroscopy, light of a specific wavelength (often a lamp of the metal being analyzed, to ensure the wavelength is correct), instead of heat is used to move electrons up energy levels. This time, the amount of light absorbed is measured and compared with the amount absorbed by standard solutions. This only works for metals and is quantitative analysis only as it must be known what metal ions are being analyzed (as only then can you choose an appropriate wavelength). Other metal ions do not affect the result as they absorb different wavelengths.

In UV-visible spectroscopy, which is very similar to atomic absorption spectroscopy, light of a specific wavelength is chosen. This wavelength must be one at which the substance being analyzed absorbs strongly at, and at which other substances present absorb little or not at all. You may be given a absorbance (generally no scale given) vs wavelength graph and be required to choose the wavelength of light at which the test should be conducted. The amount of light absorbed is measured and, like in AAS, compared with the amount absorbed by standard solutions to determine the concentration. This works for more than just metals, it works for all 'coloured' compounds (for the purposes of UV-visible spectroscopy, this means any compound that absorbs light of some wavelengths strongly and at other wavelengths weakly).

IR/NMR/mass spectroscopy doesn't have much to do with electron energy levels, or wavelengths absorbed/emitted by specific wavelengths (i think)