Development of the atomic theory

1. Development of the atomic theory By: Ruan “the amazingly great one” Meyer

2. Democritus • In 440 B.C. Democritus proposed: • the idea of an atom • that eventually an object could be cut until it reached a particle that could no longer be cut • the name of this particle as an “atom” from Greek atomos, the word for indivisible • that this “atom” was a pure substance that was hard and small and that they are always moving and that they form different materials by joining together

3. John Dalton • In 1803 Dalton released his own atomic theory that stated: • 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 from different elements are different • atoms join with other atoms to make new substances

4. J.J. Thompson • Thompson made a discovery in 1897 that included: • he discovered that atoms were made up of even smaller particles and therefore an atom could be divided • he discovered electrons, which he first named corpuscles • he created a model, the plum-pudding model, that was a possible organization of an atom

5. Ernest Rutherford • In 1909 a former student of Thompson’s tested his theory. This is what Rutherford found: • he tested the “plum-pudding” theory by launching extremely small particles at a sheet of gold • his results indicated that an atom has a positively charged center and space between this “nucleus” and the electrons • Rutherford modeled a surprisingly accurate, new model of an atom

6. Neils Bohr • In 1913, Bohr suggested an idea while he worked with Rutherford: • he theorized that electrons orbit the nucleus on distinct paths and not at all between them • he also thought that atoms could freely jump to different paths, but still not between them

7. James Chadwick • In 1932, Chadwick made another important discovery: • he found that in the nucleus of every atom, there were neutrally charged particles, as well as the positive protons

8. The end of the beginning • Much like atoms are the most basic building block of all matter, these discoveries formed the basis of atom research and led to the last fine tuning that shaped the way we know atoms today. All of these scientists played an important role in the entire field of science, in addition to all the other scientists who worked for the knowledge we have today.