Transcript
Know the following about the EM spectrum:
• visible, infrared, and UV regions• describe the variation in:– wavelength– frequency– energy– colors for visible light
The electromagnetic spectrum
Know what is in the red
boxes
The Electromagnetic Spectrum
High frequency
Short wavelength
High energy
lower frequency
longer wavelength
lower energy
• continuous spectrum–produced by light as it passes through a
prism• in the case of white light, all colors are seen• there are no levels
• emission line spectrum–energy is applied to a specific element• this “excites” the element and the light is viewed
through a spectroscope– a continuous spectrum is NOT observed, but a series of
very bright lines of specific colors with black spaces in-between instead
– unique for every element and are used to identify atoms (much like fingerprints are used to identify people)
More on emission line spectrum
Give off energy when falls back
down to normal energy
level
– the process• electrons surround the nucleus in specific orbitals
or energy levels• when electrons are excited (heat/electricity) they
can move to a higher energy level• when they move back down they emit energy in
the form of electromagnetic radiation• because electrons can only exist in certain energy
levels, only certain transitions can occur• the color of the light emitted depends on the
frequency of the emitted photon• http://www.youtube.com/watch?v=QI50GBUJ48s
1. an electron in the atom gains (absorbs) energy from heating
2. electron jumps up an energy level.
3. electron is now unstable (unwelcome) in this level and is “kicked out”
4. when the electron loses the energy and come back to the original level, light is emitted
this is a repetitive slide- just couldn’t bear to delete it
The Atomic Emission Spectrum of Hydrogen
• the emission spectrum of hydrogen is the simplest emission spectrum because there is only one electron– if had more than one electron, they would influence the
other’s position– it is not uniform, but concentrated into bright lines,
indicating the existence of only certain allowed electron energy levels
– Electron “jumping” website– McGraw Hill animation link
convergence up here
(levels are close
together)
More about energy levels• energy levels of atoms are NOT evenly spaced like
the rungs of a ladder– the higher the energy level, the smaller the
difference in energy between successive energy levels becomes
– the energy difference between levels becomes less as the level number increases
– this means that the lines of a spectrum will converge (get closer together with increasing energy)
IB-- this is referred to as convergence of the
spectral lines
This is referred to as convergence of the
spectral lines.
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