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450 BCE
450 b.c
In 450b.c a man named Empedocles came up with the 4 element model. Empedocles tested this model by doing his own experiments. -
400 BCE
400 b.c
In 400b.c a man named Democritus came up with the atomic model. Democritus never tested this model as nobody beleived this theory was true. -
350 BCE
350b.c
In 350b.c a man named Aristotle didn't come up with a model or theory however, he did believe in the 4 element model. He didn't test his belief, but he influenced many people to believe in his theory. -
Period: 1500 to
1500-1600A.D
In 1500-1600 many alchemists believed that metals grew like plants, ripening into gold. They did many experiments trying to turn cheap metals into gold, by dividing chemical symbols which we now call elements and compounds. They also invented many lab tools that we use presently. Despite finding some new substances they still accepted the 4 element model. -
1650
In 1650 an english scientist named Robert Boyle did not believe in the 4 element model. He invented a new definition of an element. The definition was: "I mean by element, simple unmitigated bodies". The more modern version of this definition is "a pure substance that cannot be chemically broken down into simpler substances".Boyle believed that air was a mixture instead of an element. -
Late 1700
A man named Joseph Priestley was the first person to isolate oxygen, in a scientific way. Priestley did not know oxygen is an element, which was soon recognised by a man named Antoine Lavoisier. As Lavoisier was experimenting with Priestley oxygen he concluded that air is a mixture of at least 2 gases, 1 being oxygen. -
Late 1700s
Henry Cavendish experimented mixing metal with acid which resulted with a flammable gas that was lighter than air. Cavendish didn't know at the time that the gas was called hydrogen. However he did realise that his gas would burn if put with Priestley's oxygen which would turn into water. Until that discovery, scholars still believed water was an element. -
Late 1800s
In the 1800's Dalton's model didn't explain why you get a spark when you touch a metal doorknob on a dry winter day. Therefore a new model was created, introducing negatively charged particles that could be separated from atoms and moved to other atoms. -
1808
In 1808 majority of people decided matter was made of element. A man named James Dalton made a theory about why elements are different from each other and from "non-elements". Dalton's atomic model stated:
-All matter is made of atoms
-Each element has its own kind of atom, along with its own particular mass
- Compounds are created when atoms of different elements of different elements link to form molecules
-Atoms cannot be created, destroyed, or subdivided in chemical change -
1831
In 1831 a man named Micheal Faraday found that in some substances and compounds, electric current could cause chemical changes. The atoms could become charged atoms called ions, by gaining electric charges. In a modified version of Dalton's model:
-Matter has to contain positive and negative charges
-Opposite charges attract and like charges repel
-Atoms combine to form molecules because of electrical attractions between atoms. -
1904
In 1904, a man named J.J Thompson investigated the atomic model further to help explain his new discovery of negative light particles, or also known as electrons. Thompson did some experiments using beams with much heavier positive particles. This new model is known as the "raisin-bun" model. A japanese scientist named H.Nagaoka, who worked around the same time modelled the atom differently. He modelled the atom as a large positive sphere surrounded by a ring of negative electrons. -
1911
In 1911,a man named Ernest Rutherford who worked in McGill University in Montreal designed an experiment to test Thompson's and Nagaoka's models. He used a type of radiation called alpha particles that he aimed at a thin sheet of gold foil. He predicted based off the raisin-bun model the particles will pass through the foil,which most did. There were a few of the alpha particles bounced almost straight back from the foil. From this discovery Rutherford made a new model called the nuclear model.
