Electrons “in Orbit” Topic 2.1

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 vs. Line Spectrum

• 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.