Matter timeline

Greek scholar Empedolces proposed that matter was made of 4 elements, water, earth, fire and air. He believed that these elements mixed together in different amounts result in different substances. Different to most philosophers of his time he liked test his theories experimentally.

Empedocles was a Greek scholar who proposed the theory that matter made up of 4 elements. These elements were earth, water, air and fire. The theory also stated that these elements mixed together in different amounts result in different substances. Also unlike most philosophers of his time he liked to test his theories experimentally.

Another Greek named Democritus proposed a theory that matter was made of tiny particles that could not be broken down further. He called these particles atoms. He named them after the Greek word atomos which means indivisible. However his theory was never accepted because Socrates was a very influential figure and he didn't accept them at the time.

A philosopher named Aristotle agreed with Empedocles four element model and since he was very influential and his writing was read by many people that the four element model was approved for almost 2000 years later,

At this time many alchemists believed that metals grew like plants and for centuries they tried numerous experiments trying to prove it. They tried to turn cheap metals like iron and lead into gold but they never deemed themselves successful at this. However in this time-span they devised chemical symbols for elements and compounds, they invented beakers, filters, stirring rods, distillation apparatus and many other laboratory tools used today.

Robert Boyle was an english scientist who did not believe in the four element model. He made a new definition for the word element: "I mean by element, simple unmitigrated bodies." Today the modern version of that is: a pure substance that cannot be chemically broken down into simpler substances. He also proved that air was not an element but a mixture.

Joseph Priestly was the first person to isolate oxygen scientifically, at the time he didn't know that oxygen was an element. This was later brought to attention by Antoine Lavoisier, he concluded that air is a mixture of two gases one of which was oxygen. Meanwhile Henry Cavendish was experimenting mixing metal with acid which resulted in gas lighter than air, his gas would burn in some of Priestley oxygen and would result in water. Until then scholars believed that water was an element.

By this time it had been accepted that matter was made of elements. John Dalton published a theory of why elements differ from each other and non-elements. The model stated that:
- All matter is made up of atoms which are particles too small to see with the human eye
- Each element has unique atom with its own particular mass
- compounds are created when different atoms from different elements link to create molecules
- Atoms cannot be created, destroyed or subdivided during chemical changes

Micheal Faraday discovered that electric current could cause chemical changes in some compounds in solution. The atoms can gain electric charges and form ions which are charged atoms. In his model:
- Matter must contain positive and negative charges
- Opposite charges attract and like charges repel
- Atoms combine to form molecules because of electrical attractions between them

JJ Thompson revised the atomic model to explain his new discovery of very lights negative particles called electrons. He also discovered protons which are heavier positive particles. The new model stated:
- Atoms contain particles called electrons
- Electrons have a small mass and a negative charge
- The rest of that atom is a sphere of positive charge
- The electrons are embedded so that the resulting atoms are neutral or uncharged.

Ernest Rutherford tested Thomson's and Nagaoka's models. He aimed alpha particles (a type of radiation) at a thin sheet of gold foil. His prediction was that the particles would go straight through it as most of them did. However, a small number of them bounced right back. To explain this he came up with a new model called the nuclear model:
- An atom has a dense positive core called the nucleus which deflected the alpha particles
- The nucleus is surrounded by mostly empty space.