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450 BCE
Empedocles
Empedocles who was a greek scholar suggested that matter is made of four "elements". The four "elements" are earth, air, fire and water. To produce different substances, the four elements are mixed in different proportions. -
Period: 450 BCE to
Evolution of Matter
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400 BCE
Democritus
Democritus (also greek) said that matter was made of something called atoms. Atoms named after the greek word atomos meaning indivisible are particles that are so small they cannot be seen or be broken down any more than they already are. Some very influential people at time did not accept this idea however so this concept never really caught on. -
350 BCE
Aristole
Aristotle was a believer in the Empedocles matter theory. This was the theory used for almost 2000 years. -
Robert Boyle
Robert Boyle was an english scientist that didnt believe in the four element theory. He made a new definition for the word element. Element:"I mean by element, simple unmitigated bodies." He believed air was a mixture not an element. -
Joseph Priestly
Joseph Priestly did not recognize oxygen as an element but he did isolate it scientifically. Antoine Lavoisier discovered soon after that oxygen is an element. Lavoisier found that air is composed of two gases, one being oxygen. Henry Cavendish conducted experiments mixing metal with acid. This created flammable gas lighter than air. This gas that at the time they didn't know was hydrogen burned when put in Priestley's oxygen. This produced water. People now don;t believe water is an element. -
John Dalton
John Dalton who was an english chemist whos theory was about why elements and different from each other and non-elements. Here is Dalton's atomic model:
-All mater is made from atoms which are particles to small to see
-Each element has its own kind of atom, with its own particular mass
-Compounds are created when atoms of different elements link to form molecules
-Atoms cannot be created, destroyed or subdivided in chemical changes -
Micheal Faraday
Micheal Faraday discovered that some compounds in solutions had chemical changes cause by electric currents. He found charged atoms, called ions. Here's Faraday's atomic theory:
-matter must contain positive and negative charges
-opposite charges attract and like charges repel
-atoms combine to form molecules because of electrical attractions between atoms -
J.J Thompson
JJ Thompson expanded the atomic model. He discovered electrons which are very light negative particles. He experimented with beams of heavy positive particles. These were then identified as protons. The new atomic model is named the "raisin bun".
-Atoms contain particles called electrons
-Electrons have a small mass and a negative charge
-The rest of the atoms is a sphere of a positive charge
-The electrons are embedded in this sphere, so that the resulting atoms are neutral or uncharged -
Ernest Rutherford
Rutherford designed an experiment to test Thomson's model. He shot alpha particles (a type of radiation) at sheet of gold foil. Based on the "raisin bun" model he estimated that the particles would pass through the gold foil. Most of them did but a small amount of alpha particles bounced back. This lead Rutherford to come up with the nuclear model.
-An atom has tiny, dense, positive core called the nucleus
-The nucleus is surrounded mostly by empty space, containing rapidly moving negative elc.