John Dalton – developed modern atomic theory

John Dalton – developed modern atomic theory

John Dalton – developed modern atomic theory

Biography & Contributions

John Dalton was an English chemist, physicist, and meteorologist born on September 06, 1766 – died on July 27, 1844. Dalton was credited for his great works like development of modern atomic theory, law of multiple proportions, Dalton’s law of partial pressures, Daltonism.

He defined partial pressure in terms of a physical law whereby every constituent in a mixture of gases exerted the same pressure it would have if it had been the only gas present. Dalton measured the capacity of the air to absorb water vapour and the variation of its partial pressure with temperature.

He based his theory of partial pressures on the idea that only like atoms in a mixture of gases repel one another, whereas unlike atoms appear to react indifferently toward each other.

Dalton described his method of measuring the masses of various elements, including hydrogen, oxygen, carbon, and nitrogen, according to the way they combined with fixed masses of each other.

The most important of all Dalton's investigations are those concerned with the atomic theory and this atomic theory postulates about elements are made of extremely small particles called atoms, a toms of a given element are identical in size, mass, and other properties, atoms of different elements differ in size, mass, and other properties, a toms cannot be subdivided, created, or destroyed, a toms of different elements combine in simple whole-number ratios to form chemical compounds.

Dalton’s experimental measurements, allowed him to formulate the Law of Multiple Proportions.

In 1803 Dalton orally presented his first list of relative atomic weights for a number of substances. Dalton estimated the atomic weights according to the mass ratios in which they combined, with the hydrogen atom taken as unity.

Dalton's law

Dalton's law states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.

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