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Democritus atomic theory
The theory of Democritus held that everything is composed of "atoms", which are physically, but not geometrically, indivisible; that between atoms, there lies empty space; that atoms are indestructible; have always been, and always will be, in motion; that there are an infinite number of atoms, and kinds of atoms, which differ in shape, and size. Of the mass of atoms, Democritus said "The more any indivisible exceeds, the heavier it is." But his exact position on weight of atoms is disputed -
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john dalton
The crystal lattice of sodium chloride shows the sodium and chloride ions in a 1:1 ratio.
A chemist thinks of table salt as sodium and chloride ions arranged in a crystal lattice structure. Image of salt by OpenStax Anatomy and Physiology, CC-BY-NC-SA 4.0.
The law of conservation of mass says that matter is not created or destroyed in a closed system. That means if we have a chemical reaction, the amount of each element must be the same in the starting materials and the products. We use the law -
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thomson's atomic theory
Thomson atomic theory model came into existence in the year 1903. Thomson's atomic theory proposed a model of atom which is known as plum pudding model or Christmas pudding or chocolate chip cookie model. Till the end of the nineteenth century the concept of atom was similar to a small solid billiard ball. In the year 1897 Joseph john Thomson totally changed the view of an atom by discovering electron. Thomson’s atomic theory suggested that the atom is not indivisible as it was of smaller piec -
Rutherford's atomic theory
The Rutherford model is a model of the atom devised by Ernest Rutherford. Rutherford directed the famous Geiger–Marsden experiment in 1909 which suggested, upon Rutherford's 1911 analysis, that J. J. Thomson's so-called "plum pudding model" of the atom was incorrect. Rutherford's new model[1] for the atom, based on the experimental results, contained the new features of a relatively high central charge concentrated into a very small volume in comparison to the rest of the atom and with this cent -
Bohr's atomic theory
In 1913 Bohr proposed his quantized shell model of the atom to explain how electrons can have stable orbits around the nucleus. The motion of the electrons in the Rutherford model was unstable because, according to classical mechanics and electromagnetic theory, any charged particle moving on a curved path emits electromagnetic radiation; thus, the electrons would lose energy and spiral into the nucleus. To remedy the stability problem, Bohr modified the Rutherford model by requiring that the el -
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Modern atomic theory
In chemistry and physics, atomic theory is a scientific theory of the nature of matter, which states that matter is composed of discrete units called atoms. It began as a philosophical concept in ancient Greece and entered the scientific mainstream in the early 19th century when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of atoms. The word atom comes from the Ancient Greek adjective atomos, meaning "uncuttable". 19th century chemists bega
