Lesson 2.4                                       Sept. 20

Ch. 10 Electrons in Atoms

Ch. 8  Atomic Number/Mass

Ch. 11 The Periodic Table

Wave Nature of electron

frequency, wavelength, amplitude, EMR spectrum,

(300,000 km/s)

Equations (Heath p. 281)

E=hν

energy = planck’s constant x frequency

(kJ)                           (hz)

c=λν

speed of light = wavelength x frequency

Spectroscopy: (a story)

A long time ago in a land far, far away, lived a family that looked at a source of power that they thought would help them become rich.  The source of power was the sun.  To see it better they made funny glasses made of a thin glassy material.  The special glass made the bright white light change into a rainbow!

Were there other sources of energy that could be made into rainbows?

They looked at sources of elemental gasses that also produced rainbows but these rainbows were missing some colours and produced stripes of only certain colours.  They called these patterns SPECTRUMS OR SPECTRA and the special  glasses SPECTROCOPES.

How are the bright lines made?

The smart people figured out that the element’s electrons had got excited by the sun or electricity and must have absorbed energy causing them to jump up one level (QUANTA or QUANTUM LEAP) and then the electron fell back down causing an emission of energy.  Because they knew PLANCK’S formula,

E=hv, the energy must have corresponded to ….frequency of EMR.

Scientific Story

Light (or inivisible frequency) is observed coming from a source such as the sun, or an electrified gaseous element.  When you pass that light through a piece of refracting glass (spectroscope) it is broken into separate bars of light.

These separate bars (frequencies), called a spectrum, correspond to …

“quanta” of energy as calculated using Plancks equation.

Where does the energy come from?

The electrons in the particular source (H, He, O, Hg, …) had previously got excited  (absorbing energy) and now when we saw the spectrum, the electrons were giving back the energy (emission) when they fell back to their ground states.

Spectra calculations – (work sheet)

There are two basic types of spectra: emission and absorption.