Developing Models Of Matter

Particles. About 400 B.C

200

A Greek named Democritus stated that all matter was ade of tiny particles that could not be broken down. He called particles 'atoms' which means "invisible" in greek. He said that different kinds of elements contained different kids of atoms. But a lot of people did not except this theory at the time.

Aristotle. About 350 B.C

300

A philosipher named Aristotle believed 'Empedocles' "four element" Aristotle's influence on it was so big that the "four element" was excepted for 2000 years.

Alchemists

500

Many alchemists were trying to find out if you could grow metals like plants. Many of them thought that it was possible. For centuries they tryed a whole lot of expirements to grow gold off of cheap metals likeiron and lead. They made chemical symbals for many of the different substances they came up with now known as elements and compounds. However eventhough they found many new substances, they still aways excepted the 'four element' model. And they never turned lead to gold.

The True Definition of "Element"

Mar 14, 1650

A scientist from England named Robert Boyle, didn't believe in the four element model. He thought it was "I mean by element simple unmitigated bodies." This was now known as the modern definition of an element. A element was a pure substance which could not be broken down into smaller substances. He also stated that air wasn't an element but was a mixture.

Hydrogen

Mar 14, 1700

Joseph Priestly was the first person to isolate oxygen, but he did not yet know if it was an element. Another scientist named Antoine, Lavoisier was experimenting with Priestly's expiriment. He figured out that air was a mixture combination of two substances and one was air.
Another scientist named Henry Cavendish mixed a metal with an acid and it made a flammable gas that was lighter then air. which is now known as Hydrogen. He discovered that his new gas would burn in Priestly's oxygen.

Atomic Model

Mar 14, 1808

By this time it was accepted that matter was made up of elements; the two models have come together. Chemist John Dalton stated a theory of why elements differ from one another and non - elements. It stated that
- All matter is made up of atom particles too small to see.
- Each element has its own type of atom size differing.
- Compounds are made when twoor more atoms are formed together to make a substance.
- Atoms can't be destroyed, or divided to cause chemical changes.

Posative and Negative Charges

Mar 14, 1810

A new model introduced that tiny negativity charged particles could be seperated from their compound and moved to other ones. In the 1800s Michael Faraday found out that an electric current could caused chemical changes in a solution. The atoms could form electric charges and formed atoms called 'eons'. He made a modified version of Daltons model:
- Matter has to have positive and negative charges.
- Opposite charges attract to each other.
- Atoms combine to form molecules because of forces.

The Raison Bun Model

Mar 14, 1904

J.J Thomson lookedinto the atomic model farther, to explain his discovery of light negative particles called electrons. His new model became known as the "Raison Bun" model:
- All atoms contain particles that are called electrons.
- Electrons have a very small mass and negative charge.
- The rest of the atom is in a posative charge.
- The electrons are in a spher, sothe resulting atoms are neutral or uncharged.
Another Japanese scientist, modeled an atom as a large posative sphere.

An Atom's Nucleus

Mar 14, 1911

Ernest Rutherford designed an expiriment to test Thomson's model. He aimed a kind of radiation called alpha particles (posativly charged particles) at a sheet of gold. Some of the radiation particles actually bounced back. He did this to show that positive particles couldbe bounced back by negative:
- An atom has a tiny core called a nucleus (which deflected the alpha particles and contained protons).
- The nucleus is surrounded by empty space with negative electrons.

The Four Elements. about 450 B.C

Feb 13, 2000

A greek scholar named Empedocles suggested that matter was made up of four 'elements' earth, air, fire and water. These elements mixed together in different amounts to form different substances. He stated that even though air is invisible it isnt "nothing" because it takes up space. ex. Rust is 1 part fire and 2 part earth