John Dalton is considered to be the father of Modern Atomic Theory as his theory’s on atomic theory remains valid in today’s day and age. Born colour blind on September 6, 1766, in Eaglesfield, England, he earned his living for most of his life as a teacher and public lecturer. He developed the first useful atomic theory of matter around the early 19th century.[1]
Research into Gases
Dalton came with his Atomic theory as a result of his research into gases. He discovered that certain gases only could be combined in certain proportions even if two different compounds shared the same common element.[2] He found this by an experiment he performed. Dalton wondered how water and air could occupy the same space at the same time.
Dalton reasoned, If the water and air were composed of separate particles evaporation might be viewed as a mixing of water particles with air particles. 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.[3] Dalton hypothesized that the size and mass of the particles making up different gases must be different. His findings led him to hypothesize that elements combine at the atomic level in fixed ratios. He further on determined the atomic weight of each different kind of atom, by considering the number of atoms of each element present in different chemical compounds.
Dalton came with his Atomic theory as a result of his research into gases. He discovered that certain gases only could be combined in certain proportions even if two different compounds shared the same common element.[2] He found this by an experiment he performed. Dalton wondered how water and air could occupy the same space at the same time.
Dalton reasoned, If the water and air were composed of separate particles evaporation might be viewed as a mixing of water particles with air particles. 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.[3] Dalton hypothesized that the size and mass of the particles making up different gases must be different. His findings led him to hypothesize that elements combine at the atomic level in fixed ratios. He further on determined the atomic weight of each different kind of atom, by considering the number of atoms of each element present in different chemical compounds.
Dalton’s Atomic Laws or Model
The findings became the basis of Dalton’s Atomic Laws or Model. These laws focus on five basic theorems. First, matter consists of particles called atoms. Second, all atoms of the same element are identical in all respects and have the same mass. Third, atoms of different elements are totally different and have the same mass. Fourth, atoms of elements unite to form chemical compounds. Finally, atoms are indivisible and cannot be created or destroyed.[4]
This idea, explained why each gas in a mixture behaved independently. It served a useful purpose in allowing him to abolish the idea, held by many previous Greek philosopher from 460 BCE Democritus who came up with the idea that, atoms move about in a void an dare infinite numbers, unchangeable and indestructible.[5] He reasoned that atoms were the smallest part of matter, and could not be broken down further.
The findings became the basis of Dalton’s Atomic Laws or Model. These laws focus on five basic theorems. First, matter consists of particles called atoms. Second, all atoms of the same element are identical in all respects and have the same mass. Third, atoms of different elements are totally different and have the same mass. Fourth, atoms of elements unite to form chemical compounds. Finally, atoms are indivisible and cannot be created or destroyed.[4]
This idea, explained why each gas in a mixture behaved independently. It served a useful purpose in allowing him to abolish the idea, held by many previous Greek philosopher from 460 BCE Democritus who came up with the idea that, atoms move about in a void an dare infinite numbers, unchangeable and indestructible.[5] He reasoned that atoms were the smallest part of matter, and could not be broken down further.
Other Interesting Discoveries
In 1794 Dalton presented his first paper on “Extraordinary facts relating to the vision of colours” before the society. In this paper he explained that the shortage in colour perception was caused by discoloration of the liquid medium of the eyeball. He himself was a victim of colour blindness and was the first one to discover the concept. As a result ‘Daltonism’ became synonymous with colour blindness.[6] In 1803, he published his gas law which is now known as ‘Dalton’s law.’ In this law he basically stated that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.[7]
In 1794 Dalton presented his first paper on “Extraordinary facts relating to the vision of colours” before the society. In this paper he explained that the shortage in colour perception was caused by discoloration of the liquid medium of the eyeball. He himself was a victim of colour blindness and was the first one to discover the concept. As a result ‘Daltonism’ became synonymous with colour blindness.[6] In 1803, he published his gas law which is now known as ‘Dalton’s law.’ In this law he basically stated that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture.[7]
[1] BIO. 2014. John Dalton Biography. [online] Available at: http://www.biography.com/people/john-dalton-9265201?page=1 [Accessed: 6 Mar 2014].
[2] Jessa, T. 2009. John Dalton’s Atomic Model. [online] Available at: http://www.universetoday.com/38169/john-daltons-atomic-model/ [Accessed: 6 Mar 2014].
[3] [ proceeding]
Article title: The Quaker Rustic as Natural Philosopher: John Dalton and His Social Context
Author: Rocke, Alan J.. v. 1136 pp. 49-59 Date: 2013
Series: ACS Symposium Series
[4] Sharwood, J. and Corrigan, D. 2007. Nelson chemistry. South Melbourne: Thomson Learning.
[5] Egs.edu. 2014. Democritus - Ancient Greek Philosopher - Biography. [online] Available at: http://www.egs.edu/library/democritus/biography/ [Accessed: 5 Mar 2014].
[6] Ross, S. 2014. John Dalton (British scientist) :: Atomic theory. [online] Available at: http://www.britannica.com/EBchecked/topic/150287/John-Dalton/217770/Atomic-theory [Accessed: 6 Mar 2014].
[7] Chemheritage.org. 2014. John Dalton | Chemical Heritage Foundation. [online] Available at: http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/the-path-to-the-periodic-table/dalton.aspx [Accessed: 10 Mar 2014].