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Lavoisier
Lavoisier made the atomic theory of matter, stating that matter is not destroyed or created, just changes form. He burned wood, but the mass of the wood stayed the same. He also discovered Oxygen and Hydrogen -
Dalton
1) All matter is made of atoms. Atoms are indivisible and indestructible. 2) All atoms of a given element are identical in mass and properties 3) Compounds are formed by a combination of two or more different kinds of atoms. 4) A chemical reaction is a rearrangement of atoms. -
Indivisible, solid sphere model
Dalton's Theory -
Proust
Proust presented the theort that any given compound always has the same elements in the same proportion by mass. -
William Crookes
Crookes discovered the conductive nature of electricity through gasses. -
Thompson
Thompson concluded that particles were a universal component of matter Also discovered that cathode rays could be deflected by an electric field. -
Plum pudding model
Developed by J.J. Thompson -
Cathode Ray Experiment
Most research lead me to the common denominator that the Cathode Ray Tube was used for old televisions. -
Rutherford
Alpha radiation - positive charge - absorbed by a few hundredths of a cm or metal foil Beta radiation - negative charge - could pass through 100x as much foil before it was absorbed Gamma rays - no charge - could penetrate several cm of lead -
Democritus (BC)
About 400 B.C. the Greek philosopher Democritus suggested that all matter consisted of different types of small particles. NOTE: My research states that this theory is from around 400 BC and arose again some time in the early 19th century but timetoast doesnt go below 1 =( -
Antoine Henri Becquerel (1852-1908)
Antoine Henri Becquerel discovered radiation. he tried to have the chemical K2UO2(SO4)2 react with the sun. This chemical was put in a drawer for two nights. he developed the photographic plates anyway. to his surprise, there were sharp, clear pictures. He had discovered radioactivity! -
Marie Curie
Marie Curie purified radioactive ore called Radium -
Gold foil Experiment
A beam of particles, created by radioactive decay of radium, was shot onto a sheet of gold foil. the foil was surrounded by zinc sulfide. the sheet would light up when the beam struck it. -
Rutherford's nuclear atom
Obviously created by Rutherford -
Bohr
Bohr depicted the atom as a small, positively charged mucleus surrounded by negatively charged electrons. The electrons orbit around the nucleus in specific patterns. -
Electron Cloud Model
Neils Bohr and Ernest Rutherford. No specific date is specified for this model. -
Planetary/solar system model of the atom
Bohr's Model. shows electrons in a circular orbit around a nucleus -
Mosely
Mosely studied the frequencies of the x-rays given off by cathode-ray tubes when the anode was struck by electrons. -
Millikan
J.J. Thomson had previously hypothesized that the mass of a single electron
was at least 1000 times smaller than that of the smallest atom. Then Millikan performed the Oil Drop Experiment and proved his theory. This enabled him to find the charge of an electron -
Oil Drop Experiment
An "atomizer" from a perfume bottle sprayed
oil or water droplets into the sample chamber.
Some of the droplets fell through the pinhole
into an area between two plates (one positive
and one negative). This middle chamber was
ionized by x-rays. Particles that did not
capture any electrons fell to the bottom plate
due to gravity. Particles that did capture one
or more electrons were attracted to the
positive upper plate and either floated upward
or fell more slowly. -
Chadwick
Chadwick introduced the concept of the neutron to the atom. A neutron is a neutral charge in an atom's nucleus.
