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Dalton
Dalton was a chemistand wanted to know why certain proportions combine at a certain mass to form compounds. His answer was that all substances are made of atoms. Atoms are small particles that cannot be created, divided, or destroyed. Atoms of the same element are exactly alike, and atoms of different elements are different. Atoms join together with other atoms to make new substances. -
J.J. Thomson
Thomson found and showed and mistake in Dalton's theory. Thomson proved that there are small particles inside atoms. This showed that atoms can be divided into smaller parts. He used the cathode ray tube to prove this and named the negative charged particles electrons. He made a model called the plum - pudding model which had the electrons mixed throughout the atom. -
Ruthford
Ernest Ruthford was a student when he tested his teacher J.J. Thomson's work. Ruthford found that you could see where positive charged particles went after pointing them at a thin sheet of gold. But he expected the particles to go straight through the gold but some deflected and even bounced back. This proved his teacher to be incorrect with his plum - pudding model. He concluded that atoms are to be thought of mostly empty space with a small part that s highly dense. -
Ruthford
Ruthford looked at the atomic theory and he realized that the center of the atom is the dense part and it is called the nucleus. Around the positive charged nucleus are electrons and he thought electrons were a postive charge they repell from each other. -
Bohr
Bohr, who worked with Ruthford, studied the way atoms react to light. His results showed that electrons move around the nucleus in certain paths or also called energy levels. Electrons can skip from one path to another arond the nucleus. This could help predict the next step in the atomic theory. -
Schrodinger and Heisenberg
These two scientists made the path or nature of electrons more clear. The though that eletrons do not have a path and it is almost impossible to be predicted.Though there are areas where you might find electrons. This area is called the electron clouds. -
440 B.C. - Democritus
Democritus a Greece philospher thought that if you cut an object somany times you would reach a point where you cant cut that object anymore. He called this word an atom - not able to be divided. -
450 B.C. - Aristotle
Aristotle was another greek philosopher around Democritus's time. Aristotle believed that you could not end up with an object that could not be cut.
