Atomic Structure: William Crookes

Atomic Structure: William Crookes

Bibliography

What

(What happened in the exp)

• Cahier Physique - physics workbook. (n.d.). cahier physique - physics workbook. Retrieved October 2, 2014, from http://onlinephys.com/giants2.html
• Cathode ray tube and electron. (n.d.). YouTube. Retrieved October 2, 2014, from
• Crookes Tube. (n.d.). Infoplease. Retrieved October 2, 2014, from http://www.infoplease.com/encyclopedia/science/crookes-tube.html
• Lesson 8: Atoms 2: Electrons. (n.d.). History of the electron. Retrieved October 2, 2014, from http://www.furryelephant.com/content/radioactivity/discovery-electron-thomson/
• MagLab - Pioneers in Electricity and Magnetism: William Crookes. (n.d.). Retrieved October 1, 2014, from http://www.magnet.fsu.edu/education/tutorials/pioneers/crookes.html
• Sir William Crookes. (n.d.). HowStuffWorks. Retrieved October 2, 2014, from http://science.howstuffworks.com/dictionary/famous-scientists/chemists/crookes-info.htm
• Sir William Crookes' - The Atomic Structure 1861-1880. (n.d.). Sir William Crookes' - The Atomic Structure 1861-1880. Retrieved October 2, 2014, from https://sites.google.com/site/theatomicstructure18611880/sir-william-crookes/sir-william-crookes
• Welcome to...the history of the atom.. (n.d.). Welcome to...the history of the atom.. Retrieved October 2, 2014, from http://www.angelfire.com/alt2/atom/.

• reconstructed the Cathode Ray tub to find weight of thallium

• --> negative charge in atoms

• found electrons! (negatively charged subatomic particles located in electron cloud)

• cathode rays travel in a straight line

• cathode rays can be deflected

by an electric field

• cathode gave off a stream of charged particles

Who

The Experiment

• Crookes Tube (Cathode Ray Tube)

• Sir William Crookes (17 June 1832- 4 April 1919) was a British chemist and physicist
• In 1861, he discovered and named the element thallium
• He invented the Crookes tube, which resulted in the discovery of the properties of cathode rays

• electric current is applied between the electrodes

Why Did It Happen?

Crookes Tube: Purpose

New Knowledge

• "glow" is due to the interaction of electrons, which travel from the cathode to the anode, with residual gas
• cathode rays are negatively charged

• High voltage + 2 electrodes = electrons emitted from cathode
• Electrons are accelerated into anode but many miss and hit the glass
• Electrons hitting glass causes fluorescence

• electrons emitted from the cathode accelerate toward the anode

• Wanted to measure weight of Thallium in vacuum.
• Wanted to determine nature of cathode rays

Results

"Set-up"

• Identified properties of cathode rays:
• cathode rays move in a straight line, cause glass to glow, carry negative charges, and can be deflected by electric fields.
• interference of a magnet:

Relying on Information from Others

• Crookes tube: contain a positive electrode (anode) &negative electrode (cathode) sealed into a glass tube that has been at least partially evacuated
• electrical current is passed b/w the electrodes -> glow can be seen (if the residual pressure of the gas is small enough)

• In the 1830's, Michael Faraday's experiments showed that atoms have electrical components
• in 1859, Julius Plucker was the first to experiment with cathode rays produced in a vacuum

<<Cathode Ray>>