DOR: Atomic Theory 9/4 1)Which scientist is credited with the Law of Conservation of Mass? 2)This scientist performed cathode ray experiments to determine the ratio between the mass and charge of an electron. 3)This scientist found the actual mass and charge of an electron following up on another scientist’s data. 4)An electron’s location and direction cannot be simultaneously known. This statements is from _______________________________________

How did we discover electron arrangement in an atom? ELECTROMAGNETIC RADIATION ! ! !

Waves  Repeated disturbance through a medium (air, liquid) from origin to distant points.  Medium does not move  Ex. Ocean waves, sound waves

Characteristics of Waves  Wavelength  Distance between 2 points within a wave cycle  2 peaks  Frequency  # of wave cycles passing a point for a particular time unit  Usually seconds.

Wavelength and frequency are inversely proportional.

c = νλ c = speed of light, 3.0 x 10 8 m/s ν= frequency (s -1 ) λ= wavelength (nm)

Electromagnetic Waves  Produced from electric charge movement  Changes within electric and magnetic fields carried over a distance  No medium needed

Electromagnetic Spectrum  Contains full range of wavelengths and frequencies found with electromagnetic radiation  Mostly invisible, visible range (390 nnm -760 nm)  Different materials absorb/transmit the spectrum differently.

Types of Spectra  What is a spectra?  Spectrum– white light/radiation split into different wavelengths and frequencies by a prism  Continuous spectrum  No breaks in spectrum  Colors together  Line spectrum  Line pattern emitted by light from excited atoms of a particular element  Aided in determining atomic structure

Line Spectrum  Pattern emitted by light from excited atoms of an element  Specific for each element  Used for element identification

Flame Tests  Some atoms of elements produce visible light if heated  Each element has a specific flame color  Examples: Li, Na, Cs, Ca

A Bit of Quantum Theory……

Max Planck  1900  Related energy and radiation  E = hν  h= x J  s (Planck’s constant)  Quantum ---smallest amount of energy  Atoms can only absorb/emit specific quanta

Albert Einstein  1905  Added to Planck’s concept  Photons—  Bundles of light energy  Same energy as quantum  E = hν (energy of photon)  Photons release energy and electrons gain energy  Threshold frequency– minimum amount of energy needed by photon to extract electron

THEREFORE ………  Light is in the form of electromagnetic waves  Photons can resemble particles  Gave raise to the possibility of thinking about wave AND particle qualities of subatomic particles (electron)

Example 1 Calculate the energy found in a photon of red light with a wavelength of nm

Example 2 How much energy (in joules) is found in the radiation of the hydrogen atom emission spectrum with a nm wavelength?

Homework 9/4/13  Read over Law of Conservation of Mass lab procedure.  Read pp  Problems p. 293 #31  Problems p. 294 #37, 38, 41, 42