-
450 BCE
Mixing Particles
Before Christ around the year 450, Greek scholar named Empedocles discovered a theory of the 4 "elements". These elements were named "earth, air, fire and water. Empedocles proved his theory by testing air, his objective was to prove air wasn't nothing it was just invisible. -
350 BCE
Acceptance
Empedocles had the faith of The philosopher Aristotle more for the old model then the new "atomic" model. Many people believed and agreed for the "four element" and then it was accepted for 2000 years. -
400
Atoms and Particles
Democritus, also a greek, stated that it was impossible to break down the many particles of matter. Since he was inspired by the greek language, he named them "atoms" which was a name from the greek language that meant "indivisible". All the different elements were made by atoms. Shortly after, the work of Democritus was not accepted. -
Period: 500 to
Metals
Does metal just turn into gold after time? Many people do think that this theory is true. It has been proven that iron and lead have been turned into gold. They also made symbols to symbolize elements and compounds. Still, the four elements are still accepted and no one ever made gold with lead. -
Robert Boyle
A scientist named Robert Boyle did not believe the four elements and disagreed with a lot of assumptions. Robert also created a new definition for "element" that he thought made more sense. The definition that robert came up with was "A pure substance that cannot chemically be broken down into fewer substances". -
Oxygen
The particles that oxygen was composed of were found by scientist named Joseph Priestley. At the time, he did not know that oxygen was one of the elements. Antoine Lavoisier stated that air would have to be composed of at least 2 gases and one of which were oxygen. Henry Cavendish was experimenting when he mixed metal and acid and found out that hydrogen was lighter than air. -
Backing up Dalton's model
Mistakes were made in Dalton's model and it was further looked at. Shortly after another model was created and and had small negativity particles that could be separated or moved to different atoms.Micheal Faraday explained, an ion is a electric currant that could be changed chemically into compounds and solutions.
Dalton modified his model by:
-matter has positive and negative charges
-Opposite charges attract and different charges push away
-Atoms combined are called molecules -
Models
When the matter is made out of elements theory was accepted, the two models were mixed and had been put together. It was said that elements differ from each other and from non elements. John Dalton's model stated:
- Made out of small atoms -Different individual atoms- Different elements linked between molecules create compounds
-
Atomic model
J.J Thomson revised the model to prove his point even more. He explained electrons were very light negative particles. The new model was renamed "raisin bun" model.
-Atoms have particles
-Negative charged electrons have a small mass
-A positive electron is a sphere -
Testing of Models
Ernest Rutherford decided that he was gonna test both Thomson and Nagaoka's models. For Thomson's model he used alpha particles and tin foil. By using these materials the objective was to see if particles would pass straight through, most of them did but also some of them bounced right back. Ernest Rutherford created a model that was called the nuclear model.
- A atom has a nucleus
-The nucleus is around a lot of empty space