-
460
Democritus
When- ca. 460 BC
What- The universe is composed of two elements: the atoms and the void in which they exist and move.
How- He was trying to figure out how many times can you break something in half before you can break it no more.
Model Name- was not named -
Dalton
When- born September 6, 1766
What- explained the behavior of atoms based on the measurement of their weights
How- He was trying to explain why and how elements would combine with each other in fixed ratios and sometimes multiples of those ratios.
Modlel Name- Billiard Ball Model -
JJ Thomson
When- Born December 18, 1856
What- Discovered and identified the electron
How- While experimeting with currents of electricity inside of an empty glass tube to study cathode rays
Model Name- Plum Pudding Model -
Rutherford
When- Born August 30, 1871
What- Discovered a tiny, dense, positively charged nucleus that holds almost all the mass while negative, light particles called electrons circled it.
How- He sent alpha rays through a sheet of gold 1/3000 inches thick. It passed through most of the time but sometimes, it would reflect back, showing that it hit something solid.
Model name- Nuclear Model -
Bohr
When- Born October 7, 1885
What- He discovered that the electrons travel in a separate orbit around the nucleus. The number of electrons determine the element.
How- He studied light emission and figured that electrons have enough kinetic energy to travel on fixed paths. They could determine the level the electrons were rotating due to the frequency of light they were giving off.
Model name- Solar syste/ Bohr model -
Schrodinger & Heisenberg
When-August 1887 & December 1901
What- Invented mathematical formulas for quatam mechanics
How-
Model Name- Quantam Mechanical Model -
Cathode Ray Tube
What- It is a vacuum tube with a screen to view images and at least one electron gun
How- Used by JJ Thomson to observe how electric current acted -
Electron
Who- JJ Thomson
When- April 30, 1897
How- Exploring the properties of cathode rays -
Billiard Ball Model
Description- The atom is the smallest part of an element and it is an indestructable and solid unit
When- 1903
Scientists- J. Dalton -
Plum Pudding Model
Description- The pudding of the model is the positive material of an atom and the raisins are negative electrons
When-1903
Scientists- JJ Thomson -
Nuclear Model
Description- The positive particles and mass of an atom are in the nucleus. The negatively charged electrons orbit the nucleus and an atom is mostly made up of space.
When- 1911
Scientists- Rutherford -
Gold Foil Experiment
What- It was a series of tests where helium particles that were positively charged were shot at a layer of gold 1/3000 of an inch thick.
How- Used by Rutherford who saw that most particles passed through the atom but some were reflected off the gold. -
Proton
Who- Ruthrford
When- 1918
How- While experimnting with radiation and shooting alpha particles at nitrogen gas. -
Solar system/ Bohr model
Description- The electrons are placed in shells or energy levels around the nucleus
When- 1923
Scientists- Bohr -
Neutron
Who-James Chadwick
When- 1932
How- He scattered data to calculate the mass of the neutron. -
Quantam Mechanical Model
Description- Electrons exist in orbitals and orbitals differ in shape and size.
When- 1935
Scientists- Heisenburg, Schrodinger -
Works Cited
www.chemheritage.org
http://www.livescience.com/32016-niels-bohr-atomic-theory.html
dl.clackamas.cc.or.us
www.chemteam.info
www.iun.edu
http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html
http://www.nobeliefs.com/atom.htm
http://www.hyperhistory.com/online_n2/people_n2/science_n2/atomic_theory.html
chemwiki.ucdavis.edu
www.universetoday.com
www.egs.edu
http://www.tutorvista.com/science/jj-thomson-atomic-theory-0
http://www.britannica.com/EBchecked/topic/514258/Rutherford-atomic-mode
