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475 BCE
Leucippus
-Born 465BC - Died 360BC
-Leucippus was the first Greek to develop the theory of atomism.
-All apparent changes in matter result from changes in the groupings of atoms.
-There are different kinds of atoms that differ in size and shape.
-The properties of matter reflect the properties of the atoms the matter contains.
-He proposed that all matter including time and space.
-He did not experiment and had little evidence.
-His ideas was kept on by lucretius. -
465 BCE
Democritus
-Born 460BC - Died 370BC
-Leucippus, originally came up with the atomic theory, but it was then adopted by Democritus.
-The atomic theory stated that “The universe is composed of two elements: the atoms and the void in which they exist and move.”
-Democritus hypothesized that atoms are always moving, and are invisible.
-He believed that there are an infinite number of atoms. All matter consists of invisible particles called atoms. -
Jonh Dalton
-Born 1766 - Died 1844
-Dalton's atomic model set up the building blocks for others to improve on.
- He defined an atom as the smallest indivisible particle.
- Dalton's atomic theory was the first to describe all matter in terms of atoms and their properties.
-Dalton based his theory of mass and the law of composition.
-The part of his theory states that all matter is made of atoms, which are indivisible.
-theory says all atoms of a give element in mass and properties. -
Mendeleev
-Born 1834 - Died 1907
-Create the periodic table of elements.
-His period law states that physical and chemical of the elements are periodic function.
-Arranged elements into 7 groups with similar properties.
-He discovered that the properties of elements "were periodic functions of the their atomic weights" -
Goldstain
-Born 1850 - Died 1930
-In 1886 Eugen Goldstein noted that cathode ray tubes with a perforated cathode
-Emit a glow from the end of the tube near the cathode.
-Goldstein concluded that in addition to the electrons.
-The travel from the negatively charged cathode toward the positively charged anode.
-There is another ray that travels in the opposite direction
- From the anode toward the cathode.
-Because these rays pass through the holes, or channels, in the cathode. -
J.JThompson
-Born 1856 - Died 1940
-Thomson atomic model, strongly supported by Sir Joseph John Thomson.
-who had discovered 1897 the electron, a negatively charged part of every atom.
-Though several alternative models were advanced in the 1900s by Lord Kelvin and others.
- Thomson held that atoms are uniform
-Spheres have positively charged.
-Matter in which electrons are embedded.
-in which the electrons describe orbits about a tiny positive nucleus.
-Discover the electrons. -
Ernest Rutherford
-Born 1871 - Died 1937
-It was discovered in 1911 by a scientist from New Zealand named Ernest Rutherford.
-Through his clever research, Rutherford showed that the positive charge of an atom
-Is confined to a tiny massive region at the center of the atom,
-rather than being spread evenly throughout the “pudding” of the atom as Thomson had suggested.
-Discovered positives particles.
-He notted tha the particles had a charge equal and opposite on a electron. -
Niels Bohr
-Born 1885 - Died 1962
-Bohr atomic model, description of the structure of atoms, especially that of hydrogen.
-The Bohr model of the atom, a radical departure from earlier.
-classical descriptions, was the first that incorporated quantum theory.
- was the predecessor of wholly quantum mechanical models.
- The Bohr model and all of its successors describe the properties of atomic electrons.
-Explained the outer orbit of an atom could holes more elctrons that inner orbits. -
Chadwick
-Born 1891 - Died 1974
-James Chadwick discovered the neutron using evidence collected by Irene Joliot-Curie.
- who discovered that when beryllium was bombarded with positively charged.
- alpha particles a beam with a high penetrating power was created.
-James Chadwick discoverd that this beam was not deflected by either electric or magnetic fields.
- the atom itself being space in which negatively charged electrons with a mass so small it is insignificant. -
Enrico Ferm
-Born 1901 - Died 1954
-Conducted the first controlled chain reaction releasing energy from the atoms nucleus.
-Construction was completed on December 1 and the reactor went critical the next day.
-In August 1944 Fermi went to Los Alamos as a director and key consultant.
- At the Hanford site in 1944 Fermi inserted the first uranium into reactor.
-Just as he had for the first pile in the reactor two years earlier.
