Advertisement Upgrade to remove ads


*proposed that atoms are "uncuttable"
*named them after the Greek word "atomos" which means "indivisible"
*said that atoms are small, hard particles made of a single materials
*said that atoms are always moving
*Greek philosopher around 440 BC

John Dalton

*All substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed.
*Atoms of the same element are exactly alike, and atoms of different elements are different
*Atoms join with other atoms to make new substances
*Performed experiments and found that elements combine in specific proportions because they are made of individual atoms
*British school teacher and scientist in late 1700's

J. J. Thomson

*Discovered that there are small particles inside the atom and therefore atoms can be divided into smaller parts
*Experimented with a cathode-ray tube
* Plum-pudding model of the atom
*Said that the atom is mostly positiviely charged material
*electrons are small, negatively charged particles located throughout the positive material
*British scientist in 1897

Ernest Rutherford

*Gold foil experiment
*proposed that the atom has a small, dense, positively charged nucleus
*the atom is mostly empty space through which electrons travel
*electrons travel around the nucleus like planets around the sun, but their arrangement could not be described
*1909, student of Thomson

Niels Bohr

*worked with Rutherford
*suggested that electrons travel around the nucleus in definite paths
*electrons can jump from a path at one level to a path in another level
*1913 Danish scientist

Erwin Schrodinger and Werner Heisenberg

*developed Modern theory of the atom
*Austrian and German physicists
*electrons do not travel in definite paths
*there are regions called electron clouds where the electrons are likely to be found
*20th century scientists

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!



Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom


Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set