-
Period: 535 BCE to 475 BCE
Heraclitus
Heraclitus was know for his discovery in which fire forms the basic material principle of an orderly universe. He was a little bit of a pyromaniac, he thought everything was somehow made of fire. -
Period: 460 BCE to 370 BCE
Democritus
Democritus discovered the Atomic/Atomos theory in 400 B.C.He believed all matter made of small indivisible particles. He called the particles "atomos" meaning unable to cut -
Period: 384 BCE to 322 BCE
Aristotle
When the Atomic Theory was discovered Aristotle did not believe in it. He discovered the four elements that matter was made of around 450 B.C. He thought all matter was made of four elements: Earth, Water, Air and Fire. His model was believed over other philosophers because he was more popular. -
Period: to
Dalton
Dalton's Atomic Theory (1803), Is 5 main ideas that were:All matter is composed of extremely small particle called atoms.All atoms of a given element are identical in size, mass, and other properties.Atoms cant be subdivided "which means broken into smaller components", they cant be created of destroyed and that atoms are indivisible.Atoms of different elements combine in simple whole number ratio to form chemical compounds.Last in chemical reactions atoms are combined, separated, or rearranged. -
Period: to
J.J. Thomson
J.J. Thomson also discovered the Plum Pudding Model in 1897.The Plum Pudding Model is a model of atomic structure discovered by J.J. Thomson in the late 19th century.Thomson had discovered that atoms are small objects made of pieces with positive and negative charge, and that the negatively charged electrons within the atom were very small compared to the entire atom. -
Period: to
J.J. Thomson
J.J. Thomson discovered the cathode ray in 1897. In the late 19th century, J.J. Thomson began experimenting with Cathode ray tubes that are sealed glass tubes where air has been removed. A high voltage is applied across two electrodes at on end of the tube which causes a beam of particles to flow from the cathode(the negatively-charged electrode) to the anode(the positively-charged electrode). The tubes are called cathode ray tubes because the particle beam originates at the cathode. -
Period: to
Rutherford
Rutherford's Gold Foil Experiment was discovered in 1908. Rutherford's Gold Foil Experiment proved the existence of a small massive center to atoms, which would later be known as the nucleus of an atom. He experimented with positive alpha particles that are shot in a beam at a piece of gold foil. Thomson assumed that mass and charge were distributed uniformly throughout the atom. Rutherford predicted that the alpha particles would go straight through the atoms. -
Period: to
Rutherford's Importace
Rutherford is important because in 1911, he was the first to discover that atoms have a small charged nucleus surrounded by largely empty space, and are circled by tiny electrons, which became known as the Rutherford model.Thomson's experiments with cathode ray tubes helped him to discover the electron.Then Dalton thought that atoms were indivisible particles, and Thomson's discovery of the electron proved the existence of subatomic particles. -
Period: to
Bohr
Bohr's Diagram was discovered in 1913. Bohr's diagram was about the Line Emission spectrum- the colors of light released when electrons move from the excited state to the ground state. When electricity runs through the glass tube, electrons gain energy. It is called the excited state because electrons jump to higher energy sublevels with the energy gained. when the electrons drop back to their ground state in a lower energy sublevel, they lose the energy they had gained in the form of light. -
Period: to
Schrodinger
Schrodinger's Electron Cloud Model was discovered in 1926. The Schrodinger Electron Cloud Model, showed that electrons don't "orbit". we don't really know where electrons are in the "electron cloud" outside the nucleus. We have probabilities of where they might be located we care about how much energy the electrons have. We use electron energy levels to show us how much energy the electron has relative to the nucleus. -
Period: to
Chadwick
Chadwick discovered the Electron Cloud Model 2.0 in 1932. In Chadwick's Electron Cloud Model 2.0 he knew that he was looking for a neutral subatomic particle to account for all the "extra mass" within the nucleus not from the protons using different metals and hitting them with alpha particles, led to the release of the neutral subatomic particle later called the neutrons. -
Period: to
Chadwick's importance and findings