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370
Democritus
He lived in 400 BC. First to suggest that materials were made up of smaller things. He called them 'Atmos' and stated that matter cannot be created or changed. He was the first to develop democracy. -
Period: 370 to
Scientists Timeline
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Antoine Lavoisier
Known for his expirementation skills. Came up with the Law of Conservation, which states matter cannot be made,nor destroyed. Also hinted at the rearrangement of matter in reactions. He was suspected of treaon during the French Revolution. -
John Dalton
Created Dalton's Theory, which states:
1.) Matter is composed of extremely small particles called Atoms.
2.) Atoms are indivisible and indestructable.
3.) Atoms of a given element are identical in size, mass, and chemical properties.
4.) Atoms of specific elements are different then those of other elements,
5.) In a chemical reaction, Atoms seperate, as well as combine/rearrange.
John Dalton was a Quaker. -
J.J. Thomson
J.J. Thomson created the Cathode Ray, which made him able to test the polarity of atoms by placing a magnet next to the Cathode Ray. Doing this made him discover that there were negatively charged particles, and isd credited for discovering electrons. He was knighted in 1908 by King Edward VII. -
Marie Curie
Marie Curie reported that radioactive materials caused atoms to spontaneously break down. When they broke down, they released radiation in the form of energy and substomic particles. -
Max Planck
He used the idea of discrete units of energy to explain hot, glowing matter and developed the original Quantam Theory. -
Albert Einstein
He established the General Theory of Relativity. He had also proposed that light energy can be absorbed in packets called Quanta. In 1905, all of this led up to him mathematically proving the existence of the Atom. -
Robert Millikan
Millikan determined the charge of a unit, which allowed the calculation of the mass of the electron and positively charged atoms. -
Ernest Rutherford
Ernest Rutherford's first contribution to the Atomic Theory was the Alpha particle (a=He^+2), positive, the Beta particle (B=e-), negative, and a Neural particle (Y), light. -
Ernest Rutherford
Ernest Rutherford's second contribution consisted of the statement that atoms had a small, dense core, which he named a nucleus. -
Niels Bohr
He proposed that electrons existed in set levels of energy, orbiting around the nucleus. He stated that if it radiated energy, it would move closer to the Nucleus. This was a giant step forward for the Atomic Theory. HIs son, Aagae, won a Nobel Prize. -
Louis De Broglie
He is the scientist who discovered wave lengths, for which he was highly praised by Albert Einstein. Because of this, he was able to deduce that matter could show wave-like properties. -
Werner Heisenberg
Werner founded Quantum Mechanics, but is known for the Uncertainty Principle, which states the exact location and energy of an electron cannot be determined simultaneously. When finding one exact value, the other will always be uncertain. -
Erwin Schrodinger
Schrodinger found that the Bohr model was only one-dimensional and used one quantum number. Schrodinger allowed three quantum numbers, making it three-dimensional. Doing this with mathematical equations described the likelyhood in which an electron would be found occupying a certain space. -
James Chadwick
James Chadwick's was born in Cheshire, England, in 1891. contribution to the Atomic Theory was that he proved the existence of neutrons. He did this by bombarding Berylllium with alpha rays. He was a prisoner of the war in Germany.
