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Aristotle didn’t believe that atoms were of different sizes and had regular geometric shapes. He believed everything consisted of fire, earth, air, and water.
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He stated that atoms are the building blocks for all things and that atoms are tiny, indivisible, and differ only by shape and arrangement.
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Atomic Theory:
- All elements are composed of tiny idivisible 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 proportions.
-Chemical reactions occur when atoms are separated, joined, or rearranged. -
Studied the effect of electricity on solutions, coined term "electrolysis" as a splitting of molecules with electricity, developed laws of electrolysis.
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Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights".
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Proposed that electricity was made of discrete negative particles he called electrons.
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Discovered electrons with a cathode ray tube.
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Used the idea of quanta (discrete units of energy) to explain hot glowing matter.
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Postulated a "Saturnian" model of the atom with flat rings of electrons revolving around a positively charged particle.
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Determine the unit charge of the electron with his oil drop experiment.
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Rutherford proposed that all of the positive charge and all of the mass of the atom occupied a small volume at the center of the atom and that most of the volume of the atom was empty space occupied by the electrons.
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Rearranged the periodic table by atomic number not atomic mass.
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Discovered the existence of isotopes through the use of a mass spectrograph.
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His atomic model had atoms built up of sucessive orbital shells of electrons.
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Discovered that electrons had a dual nature-similar to both particles and waves.
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On the basis of the multiplet structure of the atomic spectra and the anomalous Zeeman effect, which was not able to be interpreted for a long time, Pauli realized that the peculiar, classically non-describable type of ambiguity of the quantum theoretical properties of the luminous electron demands for its description a fourth quantum number.
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Hund's rule states that orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second electron, and all electrons in singly occupied orbitals must have the same spin state.
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He calculated the behavior of electrons, and subatomic particles that also make up an atom.
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Viewed electrons as continuous clouds and introduced "wave mechanics" as a mathematical model of the atom.
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He discovered the neutron.
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Conducted the first controlled chain reaction releasing energy from the atoms nucleus.
