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400
Democritus
He proposed the idea that matter was not infinitly devisiable. He believed that matter was made up of tiny particles. -
Period: 400 to
Atomic Theory
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Antoine Lavoisier
Proposed the Law of Conservation of Mass. And stated that matter is neither lost nor gained during a chemical reaction. -
John Dalton
Proposed the atomic theory of Matter. Reasoned that elements were composed of atoms and only whole numbers of atoms can combine to form compounds, -
Solid Sphere Model
The atom is a solid sphere that cannot be divided up into smaller particles or pieces. -
J Plucker
He built the first Cathode Ray tube, which are used for X-rays. -
J.J Thomason
He discovered the electron. And reasoned that atoms contain negatively charged particles, which he called electrons. -
Plum Pudding Model
The atom can be divided up into a fluid which is stated as a "pudding" and electrons as well. The atom is mostly made up of fluid, that spreads out in the atom that has a postive charge. And the electrons are negatively charged. -
Ernest Rutherford
Shot tiny positive charged particles at a thin gold foil. He observed that most of the alpha particles went through the foil but few bounced back. And reasoned that there was a massive and postively charge in an atom, called the nucleus. -
Nuclear Model
The atom can be divided into the nucleus and electrons. The nucleus is in the center of the atom and has a positive charge. The electron circle the nucleus and have a negative charge. -
Neils Bohr
Developed a model of an atom that explained the light given off when elements are exposed to flame or electric fields. He reasoned that the electrons orbit around the nucleus., the electrons in the orbits have different energies. -
Solar System Model
The atom can be divided into a nucleus and electrons. The nucleus is massive and posively charged. The electrons circle around the nucleus in orbits. The electrons also orbit at a distance from the nucleus. -
Proton Model
The nucleus contains protons. Protons are postive charges. The electrons circle around the nucleus and most of the atom is empty space. -
Werner Heisenberg
Proposed a cloud model of an atom. He suggested that the location of an electron could not be specified precisely. And the cloud model indicates where you will most likely find a single electron. -
Electron Cloud Model
An electron cloud surrounds the nucleus, the cloud is made up of fast moving electrons. And the nucleus is made up of protons and neutrons. -
James Chadwick
Found that the nucleus also included uncharged, or neutral, particles, which he called neutrons. He reasoned that the neutrons were important in holding the positively charged protons together. -
Aristotle
Stated that empty space cannot exist and matter is made of the earth, fire, air, and water.
