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460
Democritus
Democritus
Democritus was born in Abdera in 460 BC
Democritus discovered that:
* All matter consists of invisible particles called atoms. Everything else is called the void.
* Atoms are indestructivle.
* Atoms are eternal and have been and always will be, in motion
* Atoms are homogenous
* Atoms differ in size, shape, mass, position, and arrangment
Democritus lived from 460 BC to 370 BC -
John Dalton
John Dalton John Dalton was born on Sep. 6, 1766.
Dalton's atmoic theory:
* All matter is made of small, individual atoms
* Believed atoms of different elements could be distinguished based on their different atomic weights.
* The molecules of an element were always made up of the same proportions.
* The atoms within a given element were the exact same size and weight.
Created a table listing all the atomic weights of all known elements -
J.J. Tompson
J.J. ThomsonJ.J. Thompson was born on Dec. 18, 1856 in Cheatham Hill, near Manchester in the United Kingdom
* Thomson came up with the Cathode Ray Tube
* Concluded that electrons were apart of the atom.
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Ernest Rutherford
Ernest RutherfordRutherford lived in New Zealand and won a noble peace prize in chemistry.
Rutherford's diagram of an atom is the protons and nuetrons in the nucleus and the electrons orbiting.
Element was named in his honor
Studied radioactivity. Came up with terms "alpha" and "beta" -
Francis Aston
Franciss Aston 2Francis Aston
Studied creation of x-rays
Assisted JJ Tomphson in Cambridge
Discovered large number of isotopes using mass spectrometer
formulated the "whole number rule -
Niels Bohr
Niels Bohr 2Niels BohrBorn in Copenhagen, Denmark.
Studied theoretical nuclear physics.
Bohr's model of the atoms shows a small positively charged nucleus surrounded by orbiting electrons.
Discovered electrons travel in seperate orbits
Borhium is named after him, an element in the periodic table.
Came up with Quantum Theory -
James Chadwick
James ChadwickBorn in Chesire, England.
Discovered the neutron and studied nuclear physics
