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Transcript of Atomic Timeline
Millikan determined the charge and mass of sub- atomic particles. He started experimenting in 1909 and determined the electic charge of an electron first. Howerver, the results were not acurate enough so he did the oil drop experiment and obtained more pricise results. Millikan also came up with equations that gave the charge of electrons and protons.
Democritus was one of the first to discover the existence of atoms. His contribution helped scientists understand the idea of an atom. Democritus's model and ideas helped scientists further research the science and the make up of atoms. His model was a round sphere with no electrons, protons, or neutrons.
Democritus's atomic ideas
All matter consists of invisible particles called atoms.
Atoms are indestructible.
Atoms are solid but invisible.
Atoms are homogeneous.
Atoms differ in mass, size, shape, position, and arrangement.
The modern discovery of atoms began with John Dalton. He used chemical methods to turn Democritus's ideas into a scientific theory. Dalton based his studies on the ratios in which elements combine in chemical reactions. The results of his experiments led him to create a theory known as Dalton's Atomic Theory.
Dalton's Atomic Theory
All elements are composed of tiny, indivisible particles called atoms.
Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
Atoms of different elements can physically mix together or can chemically combine in simple whole number ratios to form compounds.
Chemical reactions occur when atoms are separated from each other, joined, or rearranged in different combinations. Atoms of one element, however, are never changed into atoms of another element as a result of a chemical reation.
JJ Thompson discovered the electron. He performed experiments that involed passing electric current through gases at low pressure. Thompson's model was a positively charged sphere with electrons in it. His model was called the "Plum-Pudding Model."
Ernest Rutherford discovered that atoms have a positively charged nucleus. He completed the gold-foil experiment. His results led him to believe that an atom is mostly empty space. Rutherford's atomic model is known as the nuclear atom. The protons and neutrons are in the nucleus making it positively charged. The electrons are around the nucleus and takes up almost all the volume of the atom.
Bohr said that electrons move in a circular orbit at certain distances from the nucleus.
Schrodinger invented equations to explain the motion of electrons in atoms. The solutions to his equation are the energies, or energy levels of electrons. His equations led to what is known as the Quantum Mechanical Model. The Quantun Mechanical Model shows the modern dipiction of an atom.
Chadwick affrimed that nuetrons do exist. Scientists now knew that the nucleus had positivly charged protons and subatomic particles with no charge, called neutrons, in it.
Max Planck proposed the Quantum Theory in 1900. His findings led Niels Bohr to create a new model of the atom.
Eugene Goldstein discovered canal rays, also called postive rays. He is also credited with the discovery of the proton.
Albert Einstein was the first person to show a way to prove the existance of atoms. Since the atomic theory says that any liquid is made up of molecules, Einstein realized that invisible molecules would produce change.
Dmitri discovered that the properties of elements "were periodic functions of the their atomic weights."
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Crookes recontructed the cathode ray that helped lead to the dicovery of the electron. From the Crookes tube he pulled out some objects have a negative charge while hitting the tube.
Geiger Developed an electrical device to "click" when hit with alpha particles.
Lavoisier began to really talk about what the atom was. He came up with the law of conservation. He was known for his experimental skills.
By: Kassady Fryer and Chrissy Byrd