6.9.11

Happy Birthday John Dalton

John Dalton, born September 6, 1766, was an English chemist known for his Atomic Theory which had the following five points:

  1. Elements are made of tiny particles called atoms.
  2. All atoms of a given element are identical.
  3. The atoms of a given element are different from those of any other element.
  4. Atoms of one element can combine with atoms of other elements to form compounds. A given compound always has the same relative numbers of types of atoms.
  5. Atoms cannot be created, divided into smaller particles, nor destroyed in the chemical process. A chemical reaction simply changes the way atoms are grouped together.  

Unfortunately, Dalton had an additional statement that prevented his theory from being accepted for many years: When atoms combine in only one ratio, "..it must be presumed to be a binary one, unless some cause appear to the contrary."

Dalton had no evidence to support this statement from his theory and it caused him to wrongly assume that the formula for water was OH and ammonia was NH. Because of this, Dalton's experimental data did not support most of the conclusions he drew from it.

Amazingly, all but two of the 200 year old statements in Dalton's Atomic Theory are still believed to be true by scientists today. The statement "Atoms cannot be subdivided, created, or destroyed into smaller particles when they are combined, separated, or rearranged in chemical reactions" is inconsistent with the existence of nuclear fusion and fission, although such processes are nuclear reactions, not chemical reactions. In addition, the statement "All atoms of a given element are identical in their physical and chemical properties" is not precisely true, as the different isotopes of an element have varying numbers of neutrons in their nuclei, though the number of protons remains consistent.

Dalton's method for representing the "elements or ultimate particles"

Figure name weight
  1. Hydrogen 1
  2. Azote 5
  3. Carbone or charcoal 5
  4. Oxygen 7
  5. Phosphorus 9
  6. Sulpher 13
  7. Magnesia 20
  8. Lime 23
  9. Soda 28
  10. Potash 42
  11. Strontites 46
  12. Barytes 68
  13. Iron 38
  14. Zinc 56
  15. Copper 56
  16. Lead 95
  17. Silver 100
  18. Platina 100
  19. Gold 140
  20. Mercury 167
  21. An atom of water or steam, composed of 1 of oxygen and 1 of hydrogen, retained in physical contact by a strong affinity, and supposed to be surrounded by a common atmosphere of heat; its relative weight = 8 
  22. An atom of ammonia, composed of 1 of azote and 1 of hydrogen -6
  23. An atom of nitrous gas composed of 1 of azote and 1 of oxygen - 12
  24. An atom of olefiant gas, composed of 1 of carbone and 1 of hydrogen-6 
  25. An atom of carbonic oxide composed of 1 of carbone and 1 of oxygen -12
  26. An atom of nitrous oxide, 2 azote + 1 oxygen - 17
  27. An atom of nitric acid. 1 azote + 2 oxygen -19
  28. An atom of carbonic acid, 1 carbone + 2 oxygen-19
  29. An atom of carburetted hydrogen, 1 carbone + 2 hydrogen-7
  30. An atom of oxynitric acid, 1 azote + 3 oxygen-26
  31. An atom of sulphuric acid, 1 sulphur + 3 oxygen-34
  32. An atom of sulphuretted hydrogen, 1 sulphur + 3 hydrogen - 15
  33. An atom of alcohol, 3 carhone + 1 hydrogen - 16
  34. An atom of nitrous acid, 1 nitric acid + 1 nitrous gas - 31
  35. An atom of acetous acid, 2 carbone + 2 water - 26
  36. An atom of nitrate of ammonia, 1 nitric acid + 1ammonia + 1 water-33
  37. An atom of sugar, 1 alcohol + 1 carbonic arid - 35

2 comments:

A442 said...

Very interesting, as always. At school I only learned the basic concept of Dalton's Atomic Theory: An atom is a solid indivisible particle.

Ds said...

I'm glad you enjoyed it.