atomic theory timeline

Events

democritus

Approx. 400 bc

Born in Abdera, Thrace
He was a Greek philosopher who believed that the universe was made of tiny " uncuttable " particles.
believed everything is composed of small atoms moving in a void
atoms are indivisible and indestructible
ideas were rejected by leading philosophers
his model was a round spherical ball

John Dalton

1766

born in Eaglesfield, Cumbria
known as The Father of the Modern Atomic Theory .He came up with the atomic theory, which states that matter is made up of atoms. He hypothesized that atoms of a given element are identical, as well as a tiny hard sphere.
believed that All matter is composed of extremely small particles called atoms.
All atoms of a given element are identical, having the same size, mass and chemical properties. Atoms of a specific element are different from those of any other element.
Atoms cannot be created, divided into smaller particles, or destroyed.
Different atoms combine in simple whole number ratios to form compounds.
In a chemical reaction, atoms are separated, combined or arranged.

J.J Thomson

1856

made the plum pudding model of an atom. its a ball of positively charged material with negatively charged particles floating around inside.
believed that "All matter has tiny, negative particles" and Experimented with cathode ray tube (CRT)

ernest rutherford

1871

born in New Zealand
He discovered that atoms are mostly empty space and that the proton has a positive charge. He did the Gold Foil experiment.
believed that an atoms mass is mostly in the nucleus
the nucleus has a positive charge (moseley)
electrons in a fixed orbit (WRONG)

niels bohr

1885

Born in Copenhagen
He created a model of the atom in which electrons moved around the nucleus in a fixed orbit.
believed that nucleus surrounded by orbiting electrons at different energy levels used quantum energy theory
worked on the manhattan project (Atomic bomb)
planetary model

erwin schrodinger

1887

Born in Vienna, Austria
Proposed that a wave equation could be used
to describe the behavior of an electron in the same way that a wave equation could be used to described the behavior of light
Believed that you cannot predict the set path of an electron and that they basically fly around in electron clouds

james chadwick

1891

born in Bollington, England
Discovered the neutron. He was the head of British scientists who worked on the development of the atomic bombs during WW II. He also found the missing mass of the atom's nucleus by finding the sum of the protons and neutrons.
He inspired the creation of the atomic bomb which ended World War 2. He was also the head of the British team that worked on the Manhattan project.

werner heisenberg

1901

born in Würzburg
Worked with The Quantum Theory. He discovered the uncertainty principle which is when a particle's position, energy and time can never be precisely known.
He studied the behavior of electrons and helped to make an electron cloud model based on their orbits around the atomic nucleus. He also studied other subatomic particles that compose atoms. He used matrices to determine the movement of quantum objects. He utilized quantum mechanics to better understand the behavior of particles and the atoms composed by them.

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