ATOM PRIOR TO 1900
In the 5th cent. B.C. the Greek philosophers Democritus and Leucippus proposed that matter was made up of tiny, indivisible particles they called "atom", or in Greek ""a-tomos". The reason why they assumed this is because nothing can come from nothing. Democritus believed that all atoms were firm and solid, but they could not all be the same. If all atoms were identical, there would be no satisfactory explanation of how they could combine to form everything in different shapes. Democritus concluded atom with these ideal qualities:* invisible because of their extremely small size * indivisible as their name indicates
In 1869, the russian chemist Dimitri Mendeleiev constructed a table which classified all of the chemical elements known at that time according to their chemical properties. In 1808 Dalton's A New System of Chemical Philosophy was published. This table later served to methodically classify all of the atoms, both natural and man made, by their atomic number (that is to say the number of protons that they contain). In this book he listed the atomic weights of a number of known elements relative to the weight of hydrogen. His weights were not entirely accurate but they form the basis for the modern periodic table of the elements. In the course of his studies on meteorology, Dalton concluded that evaporated water exists in air as an independent gas. Dalton reasoned that if the water and air were composed of discrete particles, evaporation might be viewed as a mixing of water particles with air particles. Solid bodies can't occupy the same space at the same time, but obviously water and air could. He performed a series of experiments on mixtures of gases to determine what effect properties of the individual gases had on the properties of the mixture as a whole. In 1904, he proposed an initial model of an atom, since nicknamed "Thompsons pudding". While trying to explain the results of those experiments, Dalton developed the hypothesis that the sizes of the particles making up different gases must be different. * solid (no void inside) * eternal because they are perfect * surrounded by an empty space (to explain their movement and changes in density) * having an infinite number of shapes (to explain the diversity observed in nature)Around 1803, John Dalton (1766-1844) developed the first useful atomic theory of matter. He imagined the atom as a sphere full of an electrically positive substance mixed with negative electron. Then in 1897, Thompson discovered the first component part of the atom: the electron, a particle with a negative electric charge.
Common topics in this essay:
John Dalton,
Democritus Leucippus,
Dimitri Mendeleiev,
Chemical Philosophy,
ATOM PRIOR,
BC Greek,
water air,
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