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Period: 300 to
timeline
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340
Aristotle
Aristotle was known for coming up with the concept of four elements. He also introduced ideas that elements are different on the basis of the properties such as hot versus cold and wet versus dry
examples
fire = hot and dry
Air = hot and wet
Water= cold and wet
Earth = cold and dry -
450
Leuccippis and Democritus
Leuccippis and Democritus were Greek philosiphers Who researched and found out that matter is composed of atoms and that they are seperated by empty spaces through which the atoms move. Atoms are solid and homogenous and they are invisible and they cannnot be changed. All the changes in matter result in changing the grouping of atoms. These two also believed that there are differnet types of atoms and also they believed the size and shape are also different. -
Robert Boyle
Robert Boyle's major contribution is that the invention Aristotle made up of the concepts of 4 elements was wrong. Boyle came up with the idea of an element and this is how he described it that it an element can not be broken down into 2 or more substances if it is that it is not an element. Robert Boyle also proposed that the sun not the earth lies at the center of the solar system. -
John Dalton
John Dalton was a english chemist, meteoroligist and physicist his atomic theory is that all matter is composed of atoms and atoms can not be made or destroyed. Also all atoms that are the same element they are all identical. However different types of elements have different types of atoms and when atoms are rearranged that means chemical reactions occured. Compounds are formed from atoms of the constituent element. -
William Crooke
William Crookes was a british chemist and physicist his main contribution to the atomic theory was Cathode Rays he discovered that rays move in astraight line and it causes the light to glow and it carries negative charges and they are capable of being deflected by the electric fields. He was also responsible for the identification and the isolation of the element Thallium. -
Max Planck
Max Planck was a German physicist who won a noble prize in 1918 for the quantum theory
Planck also thought that energy could only be absorbed or emitted in whole numbers of quanta.
How he studied his formula by studying that energy radiated from heated solids
The formula is E=hv
E= energy and v= frequency he= planck's costant -
J.J Thomson
J.J Thomson was a british physicist his atomic theory was discovering the electron. How he proved the theory: He proved using the cathode ray tube. Thomson placed two electric plates on it's path. One was positively carged and the other one was negatively charged. The glowing light bent towards the positively charged plate. He found out the glowing light was a small particle and they were smaller than the atom. This is how he found the particle called electron. -
Albert Einstein
Albert Einstein wrote five papers that changed the scientific world forever. One paper was used the quantum theory and it explained a lot involving light the was called photoelectric effect. The only way to consider light was as being composed of tiny discreet packets of enegy . He was awarded the Noble prize in 1921in physics for his explanation on photoelectric effect. -
Ernest Rutherford
Ernest Rutherford is a british chemist and physicist He was known as the father of Nuclear Physics. The Alpha particle and the beta particle and proton was named by Rutherford. Rutherford changed Thomson's atom model by performing his gold foil expirement. He proved that the atom is tiny and dense and it is positively charged core called a nucleus. All the mass is concentrated around the electrons and they circulate at some distance. -
Niel Bohr
NIel Bohr's model was that electrons travel around an atomic nucleus in a stationary orbit. His work led to different energy levels in atoms, that is if an electron drops from a higher to a lower orbit it must release energy. first shell is 2 electrons 2nd could be 8 as well as the third could be 8 -
James Chadwick
James Chadwick's contribution to the atomic theory was the discovery of the neutron. The expirement that chadwick did was he bombed beryllium with a particle to produce radial and he used the radial to bomb hydrogen and nitrogen Nuclear. The result was that that the radial was not radial anymore because it does not have momentum to produce a proton from the atom. This is how he found ot that the neutron existed.
