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400
Democritus BC
Democritus discovered that all objects are made of atoms. He discovered that atoms are invisible and super small so they can not be destroyed. He explained this by claiming the world has no empty space. The observation of the world and the objects we experienced everyday supported this answer. Democritus thought that atoms' were different in many ways. For example; atoms for liquids are smooth and atoms for sharp objects are spiky. -
470
Aristotle BC
He discoered that all matter in th eworld is made of smaller pieces because matter can be broken down. Aristotle observed his experiments of breaking down matter like plants and animals. Aristotle thought the atom looked ery tiny and undestructible. He thought that certain atoms hae a certain size and mass. He called his model the Billard Ball model or Marble model. -
Dalton
Dalton discovered that all matter is made of atoms, atoms are invisible, can't be destroyed, all atoms in a certain element are the samein mass and its properties, compounds are formed by combining two or more different types of atoms, and a chemical reaction is when the atoms rearrange themselves. Dalton made observations on the different mass of atoms by making experiments on the weightof elements. He thought the atom looked very tiny and like billard balls. -
Thomson
Thomson had discovered there are electrons in atoms. Thomson did experiments with cathobe ray tubes. The cathode rays were identical all the time regardless of the nature of the electrobes or gas used in the process. Thomson had created the plum pudding model. He thought the model looked like electrons that orbit in a cloud that is positively charged. -
Rutherford
Rutherford discovered that all the mass in an atom were in a small and positively charged ball at the center of an atom. Rutherford used the gold foil experiment to prove this. Rutherford called his model the planetary model. He thought th eatom looked like electrons that orbited around a dense central region that has a positive charge. -
Bohr
Bohr discovered that electrons move around the nucleus in a large orbits. He used the ideas of Ernist Rutherford to plan this out. He also thought about Plank's idea of quanta and put it all togehter to make his discovery. He called his model of an atom the Bohr quantum model. Bohr htought that there are electrons confined to various an ddefintie orbitals of various energies an ddiameters. -
Heisenberg and Schrodinger
Schrondinger discovered the form of probability waves that governs motion of small particles and how the waves altered by external influences. He made this discovery by studying Louis ke Brogile an dAlbert Enstein theory of relativity. Schrondinger model of an atom was called the quantum wave model. He modeled electrons as waves that show particle like behavior.
