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450 BCE
Empedocles' Theory
around 450 BC a Greek scholar named Empedocles had the idea that everything was made up of four substances: earth, air, fire and water. he called each substance an "element and it became known as the "four element theory". -
Period: 450 BCE to
Matter timeline
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400 BCE
Atomic model
a Greek man by the name of Democritus believed that all matter was made up of tiny particles in constant movement. he called the particles Atoms, after the Greek word Atomos, which means indivisible. he believed all matter was made up of different particles. this theory never really got to much attention because of Socrates; a very influential figure at the time who didn't believe in this theory. -
350 BCE
Aristotle believed in Empedocles
great influencer and philosopher, Aristotle believed in Empedocles' "four element" theory and as a result of his great influence this model was excepted for almost 2000 years -
alchemists experiments
Do metals grow like plants, ripening into gold? many philosophers and chemist believed they did for centuries before preforming numerous experiment with iron and lead trying to prove this theory, but after many attempts it was proven impossible to create gold using other cheap medals but many other substances were discovered that we now know as "Elements and compounds" as well as many lab tools that we still use to this day were also invented. but still they excepted the "Four element theory" -
Elements
an English scientist by the name of Robert Boyle, did not except the "four-element model. he came up with a new definition for the word element. 'a pure substances that cannot be chemically broken down into simpler substances' Robert Boyle also believed that air was not an element and is actually a mixture. -
oxygen, Hydrogen and water
joseph Priestley was the first person to isolate oxygen scientifically; However Antoine Lavoisier was experimenting with josephs oxygen when he came to the conclusion that air is a mixture of at least 2 gasses, oxygen being one of them. Henry Cavendish created a gas lighter than air by mixing a metal with acid, he created hydrogen and discovered he could produce water by burning hydrogen in oxygen. -
Daltons theory
as of now it is generally excepted that matter is made of elements. Daltons theory is that
- all matter is made up of millions of tiny particles way to small to see.
- Each element has its own unique particles with each their own mass
- compounds are created by linking different elements forming molecules
- no atoms can be destroyed, created or subdivided in chemical change -
negatively and positively charged
in 1831 Michael Faraday discovered that the atoms in matter can gain electric charges and form charged atoms called "ions"
- all matter has got to contain a positive and a negative charge
- opposite charges are attracted to one another and like charges fight off other like charges
- atoms merge to form molecules as a result of electrical attractions between atoms -
electrons and protons
in 1904
- j.j. Thompson discovered very light negative particles called Electrons
- he also experimented with much heavier beams of positive particles (later known as protons)
- electrons are found in atoms
Japanese scientist, H. Nagaoka models the atom in a very good way as the big positive sphere in the center surrounded by a ring of negative electrons. he used saturn as an example -
the nuclear model
Rutherford tested the previous models by experimenting with alpha particles and foil. when not all the particles passed through the foil, Rutherford came up with the nuclear model, showing that each atom contains nucleus
