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400
Arostle the idea before the atom (before 400 bc)
A greek philospher/scientist said that all things were made of four primitive Elements, Earty, Fire, Water, and Air. And that they were all shaped to link eachother. -
400
Democritus idea of the atom 400 BC
Democritus is a greek philopsher/scientist. And he got the idea of the atom which is greek for indivuisible. He stated the all mater is made of atoms, and that the matter/atoms cannot be destroyed. -
Period: to
The development of the atom
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Isaac Newton proposal (1704)
Proposed a mechanical universe with small solid masses in motion -
John Daltons Atomic Theory (1808)
Dalton stated that all elements are composed of atoms which are indivisible and indestructable. All atoms of the same element are exactly alike. Atoms of different elements are different. Compounds are formed by joining the atoms of 2 or more element. And finally stated in his theory, an atoms is the smallest unit of a element that can exist either alone or together. -
Dmitri Mendelev (1869)
Arranged elements into 7 groups with similar properties. He discovered that the properties of elements "were periodic functions of the their atomic weights". This became known as the Periodic Law. -
James Clerk Maxwell (1873)
Proposed electric and magnetic fields filled the void, of the empty spaces of the atom when they are together. -
William Crookes Cathode Ray Tube Experiment (1879)
William Crookes was a english chemist who evacuated a crooks table(Cathode Ray Tube) And sent a electrical charge through it. And saw that there are particles travelling from the cathode. He was able to show that cathode rays are negatively charged by studying the direction in which cathode rays are deflected by a magnetic field. -
E.Goldenstein (1886)
Used a CRT to study "canal rays" which had electrical and magnetic properties opposite of an electron. -
JJ Thomsons Modfified Cathode ray tube expirement (1895)
Thomson modified Crookes expirement by adding an magnetic field to it. Through this expirement Thomson saw that when particles are excited/heatd they give of particles whoch are smaller than atoms. These perticles are attractd to a positively charged object. Therefore atoms contain small negatively charged partivles called electrons -
Henri Becquerel (1896)
While studying the effect of x-rays on photographic film, he discovered some chemicals spontaneously decompose and give off very pentrating rays -
Marie Sklodowska Curie (1898)
Studied uranium and thorium and called their spontaneous decay process "radioactivity". She and her husband Pierre also discovered the radioactive elements polonium and radium. -
Ernest Rutherford Gold Foil Expirment (1899)
Ernest thorugh his experiment found that the positive charge and the mass of an atom are concentrated in a small fraction of the total volume and then derived mathematical equations for the scattering that would occur. These equations predicted that the number of -particles scattered through a given angle are proportional to the thickness of the foil and the square of the charge on the nucleus, and inversely proportional to the velocity with which the -particles moved raised to the fourth power. -
Robert Millikans Oil drop expiriment Conclusion (1909)
By repeating the experiment for many droplets, they confirmed that the charges were all small integer multiples of a certain base value, which was found to be 1.5924(17)×10−19 C, within 1% of the currently accepted value of 1.602176487(40)×10−19 C. They proposed that this was the (negative of the) charge of a single electron. -
Robert Millikans Oil drop expiriment (1909)
The experiment entailed observing tiny charged droplets of oil between two horizontal metal electrodes. First, with zero applied electric field, the terminal velocity of a droplet was measured. At terminal velocity, the drag force equals the gravitational force, and these depend on the radius in different ways, so that the radius of the droplet, and therefore the mass and gravitational force, could be determined -
Niels Bohr Atom model (1913)
Niel proposed a new model for the atom. Electrons travel around the nucleus like the planets orbit the sun kindve like our solar system. -
Ernest Rutherford naming of the Proton (1920)
Shortly after the World War I, in 1920, Rutherford proposed the name proton for the positively charged particles in the nucleus of an atom.At the same time that Rutherford proposed the name proton for the positively charged particle in the nucleus of an atom, he proposed that the nucleus also contained a neutral particle, eventually named the neutron. -
Sir james Chadwick Confirming the nuetron
Through bombarding bary lion with aplha particles. Chadwick was able to fully prove the existence of nuetrons.
