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a greek man named Empedocles made a proposition that there was 4 "element" that composed matter. they include earth, fire, water, and air. He experimented his theories to have more proof, like how although air is invisible its not nothing. it takes up space and therefor must be a form of matter.
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another greek man Democritus, presented that perhaps matter was made of tiny particles that could not be broken down. He names the particles atoms after the greek word atomos which is indivisible. Democritus's "atoms" were not widely accepted because a very influential figure named Socrates did not accept them.
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Aristotle was a very influencal philosopher who believed in Empedocles's four elements and because of this writings which were read by so many people, the four elements model was accepted fpr around 2000 years
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many alchemists believed that metals grew like plants and would ripen into gold. they experimented for centuries trying to make gold from cheap metals like iron and lead. Elements and compounds that we know of today were devised with chemical symbles for their substances. Many laboratory tools that we use today were also invented at this time.
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Robert Boyle, an english scientist did not believe in the concept of the four elements model. Therefor he came up with a new definition for the word element: "i mean by element, simple unmitigated bodies" this is now the modern definition of an element: a pure substance that cannot be chemically broken into simpler substances.
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oxygen was not known to be an element by very many people, even joseph pristley who was the first person to islate oxygen scientifically. It was finaly recognized as an element by Antoine Lavoisier. while experimenting with Priestley's oxygen he concluded that air must be a mixture of two or more gases, one being oxygen. Meanwhile Henry Cavendish was busy experimenting by mixing metals and acid. he created a flammable gas that was lighter then air, which was actually hydrogen.
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English Chemist John Dalton publishes his theory of why elements differ from each other and non-elements.
which include:
-all matter is made od atoms, which are particles too 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 -
In 1831, he found that electric currents could sometimes cause chemic changes in some compounds, the atoms were able to gain electric charges and form charged atoms, names ions. the modified bersion of dalton's model include:
- 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 -
To explain the discovery of very light negative particles, called electrons J.J. Tomson revised the atomic model further. In addition he did experiments with beams of much heavier positive particles we now know as protons, which became known as the raisin-bun model:
-atoms contain particles called electrons
-electrons have a small mass and a negative charge
-the rest of the atom is a sphere of positive charge
-the electrons are embedded in this sphere, so that the resulting atoms are neutral