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John Dalton
John Dalton (1766-1844) developed the first useful atomic theory.
Dalton's atomic theory makes the following assumptions:
1. All matter consists of tiny particles
2. Atoms are indestructible and unchangeable
3. Elements are characterized by the mass of their atoms.
4. When elements react, their atoms combine in simple, whole-number ratios.
5. When elements react, their atoms sometimes combine in more than one simple whole-number ratio. -
Period: to
Atomic theroy Timeline
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Eugen Goldstien
Eugen Goldstein (1850-1930) was a german physicist who was an early investigator of discharge tubes and is sometimes credited with the discovery of the proton.
He did experiments with cathode ray tubes, which knock electrons off atoms and attract them to a positively-charged electrode.
Goldstein's work suggested the presence of the proton -- a positively charged particle, later discovered by Ernest Rutherford. -
Joseph John (JJ) Thomson
In 1894, Thomson began studying cathode rays, which are glowing beams of light that follow an electrical discharge in a high-vacuum tube.
In 1897, Thomson showed that cathode rays were composed of a previously unkown negatively charged particle, and with that he is credited with the discovery of the electron. -
Ernest Ritherford
Ernest Rutherford is the one and only who discovered the nucleus. His theory of atoms was very important because it's the first theory which proved the existence of a nucleus in an atom where positively charged particles (protons) are segregated. This was proved by and experiment carried out by 2 students of Ernest. -
Niels Bohr
Niels Bohr was one of the most respected scientists in his generation. He was best known for his Nobel-Prize winning research on the strucutre of atoms. Bohr's greatest contribution to modern physics was the atomic model. Bohr was first to discover that electrons tracel in seperate orbits around the nucleus and that the number of electrons in the outer orbit determines the properties of an element. The chemical element Bohrium (Bh), No. 107 on the Periodic Table of Elements, is named after him. -
James Chadwick
In 1932, Chadwick made a fundemental discovery in the domain of nuclear science: he proved the existence of neutrons the elementary particle without any electrical charge this was one of the most important discoveries of the twentieth century it effectively solved the jigsaw puzzle of the atom, and earned Chadwick the 1935 Nobel Prize for Physics. -
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