John+Dalton+Hall



===** John Dalton was born on September 6th 1766. Dalton was a English chemist, meteorologist and physicist. He is best known for his pioneering work in the development of modern atomic theory.(1) In 1793, John moved to Manchester as tutor at New College founded by the Presbyterians, this is where he would study and do research that would lead to his atomic theory. (2) **===

===** It was in the early 1800s that Dalton came up with his atomic theory. In 1803 Dalton noted that oxygen and carbon combined to make two compounds. Of course, each had its own particular weight ratio of oxygen to carbon, but for the same amount of carbon, one had exactly twice as much oxygen as the other. This led him to propose the Law of Simple Multiple Proportions, which was later verified by the Swedish chemist Berzelius. In an attempt to explain how and why elements would combine with one another in fixed ratios and sometimes also in multiples of those ratios, Dalton formulated his atomic theory. (3)**===

===**"Chemical analysis and synthesis go no farther than to the separation of particles one from another, and to their reunion. No new creation or destruction of matter is within the reach of chemical agency. We might as well attempt to introduce a new planet into the solar system, or to annihilate one already in existence, as to create or destroy a particle of hydrogen." — John Dalton //A New System of Chemical Philosophy// (1808), Vol. 1, 212.**===



 * ===** All matter is made of atoms. Atoms are indivisible and indestructible. **===
 * ===** All atoms of a given element are identical in mass and properties **===
 * ===** Compounds are formed by a combination of two or more different kinds of atoms. **===
 * ===** A chemical reaction is a rearrangement of atoms. (4) **===

=== ** John Dalton was trying to find out if atoms of different elements had different masses. He then tried to determine what those masses were. Remember, he did not know the chemical formulas of any of the compounds he was working with at the time.  ** ===

** c) 1 gram of hydrogen combines with 3 grams of carbon to form methane gas.  **
=== ** Dalton reasoned that a 1 to 1 ratio of atoms was the simplest way of combining the elements and if 1 atom of hydrogen combines with 1 atom of oxygen, then oxygen must have a mass 8 times that of hydrogen.  ** ===

** The weights would thus be: hydrogen = 1, oxygen = 8, carbon = 3  **
=== ** Dalton knew the ratio of weights was correct but was his assumption of a 1 to 1 ratio correct? He had to find out. <span style="font-family: Arial,Helvetica;"> ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">He performed this test to find out. Experiment proved that 3 grams of carbon combines with 8 grams of oxygen to form a gas called carbon dioxide. He reasoned that if carbon monoxide gas had the formula CO, then carbon dioxide must be C02 (by looking at the ratio of weights.) This indicated to him that a molecule may contain more than one of a particular kind of atom in some cases. <span style="font-family: Arial,Helvetica;"> ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">Now Dalton realized that he must go back and try to find the correct formula for water (was it HO or something like H17O47 and then figure out the correct weights of atoms. <span style="font-family: Arial,Helvetica;"> ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">Water must then have the formula H20. This is better than H01/2 which meant splitting atoms, something Democritus said was impossible, until fission of atoms was accomplished with the development of the Atomic Age. <span style="font-family: Arial,Helvetica;">  ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">If 8 grams of oxygen combined with 1 gram of hydrogen, it meant that the single oxygen atom is 8 times as heavy as the two hydrogen atoms taken together. If you still set the atomic weight of hydrogen at 1, then the atomic weight of oxygen is equal to 16 (which keeps the weight ratio of 1 to 8 correct for water). <span style="font-family: Arial,Helvetica;"> ** ===

** <span style="font-family: Arial,Helvetica; font-size: 12pt;">A test for this theory would go something like this: <span style="font-family: Arial,Helvetica;"> **
=== ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">1 liter of hydrogen combines with 1 liter of chlorine to form hydrogen chloride gas. Is this gas made up of 1 atom of hydrogen and 1 atom of chlorine per molecule? Remember that Avogadro said the liter of hydrogen and the liter of chlorine contained equal numbers of particles. <span style="font-family: Arial,Helvetica;"> ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">Logic says that the number of hydrogen chloride molecules formed must only be half as many as the total number of H and Cl atoms that we started with (30 people getting married equals 15 married couples, right) so we should get 1 liter of hydrogen chloride gas. <span style="font-family: Arial,Helvetica;"> ** ===

** <span style="font-family: Arial,Helvetica; font-size: 12pt;">1 liter of hydrogen + 1 liter of chlorine = 1 liter of hydrogen chloride gas <span style="font-family: Arial,Helvetica;"> **
=== **<span style="font-family: Arial,Helvetica; font-size: 12pt;">BUT EXPERIMENTS PROVED THAT 1 LITER OF HYDROGEN + 1 LITER OF CHLORINE PRODUCED <span style="font-family: Arial,Helvetica; font-size: 13pt;">2 <span style="font-family: Arial,Helvetica; font-size: 12pt;">LITERS OF HYDROGEN CHLORIDE GAS. <span style="font-family: Arial,Helvetica;"> ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">The answer must be that one hydrogen molecule is diatomic (H2) and combines with one chlorine molecule that is also diatomic (C12). This forms 2 molecules of hydrogen chloride gas (HCl + HCl). <span style="font-family: Arial,Helvetica;"> ** === === ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">Notice that the hydrogen chloride gas molecule has a one to one ratio of atoms. H2 + C12 --> HCl + HCl (not H2Cl2 because then the product would only be 1 liter of hydrogen chloride gas and not the true 2 liters. <span style="font-family: Arial,Helvetica;"> ** ===

** <span style="font-family: Arial,Helvetica; font-size: 12pt;">4 : 32 (or reduced to 1:8) <span style="font-family: Arial,Helvetica;"> **
=== ** <span style="font-family: Arial,Helvetica; font-size: 12pt;">Dalton experimented with other elements and found "elements always combine in the same ratio by weight in making a given compound." This is the __LAW OF DEFINITE PROPORTIONS.__ <span style="font-family: Arial,Helvetica;"> ** === === **<span style="color: #000080; font-family: Arial,Helvetica; font-size: 12pt;">The Law of Definite Proportions occurs only in whole number ratios and it does not matter which mass units are used. (5) ** ===


 * Errors with Dalton's atomic theory: **
 * ** System of atomic weights was not very accurate (Oxygen had 7 instead of 8) **
 * ** Atoms can be destroyed via nuclear reactions **
 * ** There are different kinds of atoms (differing by their masses) **
 * ** Atoms can be divided into smaller particles **

(John)
Sources; 1) http://www.woodrow.org/teachers/ci/1992/Dalton.html 2) http://en.wikipedia.org/wiki/John_Dalton#Five_main_points_of_Dalton.27s_atomic_theory 3) http://dl.clackamas.edu/ch104-04/dalton%27s.htm 4) http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html 5) http://www.sciencebyjones.com/john_dalton.htm 6) http://www.buzzle.com/articles/john-daltons-atomic-theory.html 7) http://images.absoluteastronomy.com/images/encyclopediaimages/d/da/daltons-particles.jpg 8) http://3.bp.blogspot.com/_pFD3voOGUZ4/SMrGnhZcdVI/AAAAAAAAADg/GnQy7zgZLYs/s400/Dalton_atomic_symbols.jpg 9) 10)