John Dalton Atomic Theory

John Dalton was an English chemist, physicist and meteorologist. He was the first man whose proposed atomic theory was accepted. Dalton is also known as discoverer of color blindness. In the research, on the properties of atmosphere and gases in 1803, he discovered about atoms and their weights. It was published in 1805.

Dalton declared the six elements of the first table on the basis of relative atomic weights. It included hydrogen, oxygen, carbon, nitrogen, phosphorus and sulfur. He placed the hydrogen with atomic weight 1. However, he failed to confirm the reason for atomic weight. In September 1803, he found the relative weight of water, carbon dioxide and ammonia and also discovered the symbol representing the element.

In 1803, Dalton gave a lecture in London regarding the relative weight of elements. He said that an atom was the smallest particle of any element and it cannot be destroyed. Atoms of the same element are similar in weight and this weight is different in different elements. Chemical reaction is the result of rearrangement of atoms and it combines in the 1:1, 1:2, and 2:3 ratios. A chemical compound is formed by the combination of two or more different elements.

In the New System of Chemical Philosophy, Dalton issued the elements with their atomic weights and for this work he got Royal Medal in the year 1826. The mass of elements was termed as atomic weight.

After that many scientists came such as Eugen Goldstein, JJ Thomson, Ernest Rutherford and others and proposed many theories. In 1932, James Chadwick found out the electrically neutral particle and called it neutron and then the modern atomic theory was developed.