John Dalton (1766-1844), was a British chemist and physicist, who developed the atomic theory upon which modern physical science is based. Dalton was born on September 6, 1766, in Eaglesfield, Cumberland County, England. He was the son of a weaver and was initially educated by his father and then at Quaker school in his hometown, where he began teaching at the age of 12. In 1781 he moved to Kendal, where he headed up a school with his cousin and his older brother. He went to Manchester in 1793 and spent the rest of his life there as a teacher, first at New College and later as a private tutor.
In 1804 and 1809 Dalton was invited to teach at the Royal Institution in London. He was made a member of the Royal Society in 1822 and was awarded the society’s gold medal in 1826. In 1830 Dalton became one of the eight foreign associates of the French Academy of Sciences. Dalton died in Manchester on July Dalton’s most important contribution to science was his theory that matter is composed of atoms of differing weights and combine in simple ratios by weight, also known as the atomic theory.
This theory, which Dalton first advanced in 1803, is the cornerstone of modern physical cience. In 1808 Dalton’s ‘A New System of Chemical Philosophy’ was published. In this book he listed atomic weights of many known elements relative to the weight of hydrogen. His weights were not totally accurate but they did form the basis for the modern periodic table. Dalton rooted his atomic theory through the study of the physical properties of atmospheric air and other gases. During this study he discovered the law of partial pressures of mixed gases, known as Dalton’s law, that is, “The total pressure exerted by a mixture of gases is equal to the um of the separate pressures that each of the gases would exert if it alone occupied the whole
DALTON’S TABLE OF ATOMIC WEIGHTS
1. Hydrogen, its relative weight1 2. Azote 2 3. Carbone or charcoal5 4. Oxygen7 5. Phosphorous9 6. Sulphur13 7. Magnesia20 8. Lime23 9. Soda28 10. Potash42 11. Strontites46 12. Barytes68 13. Iron38 14. Zinc56 15. Copper 56 16. Lead95 17. Silver100 18. Platina100 19. Gold140 20. Mercury167
1. All matter consists of tiny particles. 2. Atoms are indestructible and unchangeable. Atoms of an element cannot be created, estroyed, broken into smaller parts or transformed into atoms of another element. 3. Elements are characterized by the mass of their atoms. All atoms of the same element have identical weights, atoms of different elements have different weights. 4. When elements react, their atoms combine in simple, whole-number ratios. Although some details of Dalton’s original atomic theory are known to be incorrect, the main concepts of the theory – those being the seperation and union as well as characteristics of atoms – are the foundations of modern physical science.
