Chemistry: Animation, Video, and Laboratory Activity

1. Democritus (440 B.C)
   

   Atom – came from the word "atomos" which means small, indivisible particles
   

1. Antoine Lavoisier (1774)
   

   Law of Conservation of Mass – mass can neither be created nor destroyed in chemical reactions
   

   Example :
   

   3.25 g + 3.32 g = 6.57 g
   

Hg(NO₃)_2(aq) + 2KI_(aq)
à HgI_2(s) + 2KNO_3(aq)

4.55 g + 2.02 g = 6.57 g

1. Joseph Proust (1799)
   

   Law of Constant Composition – Different samples of a pure chemical substance always contain the same proportion of elements by mass.
   

   By mass, water is: 88.8 % oxygen
   

   11,2 % hydrogen
   

1. John Dalton (1808)
   

   Dalton's Atomic Theory
   

   1. All matter consists of tiny particles called atoms.
      
   2. An atom cannot be created, divided, destroyed, or converted to any other type of atom.
      
   3. Atoms of a particular element have identical properties
      
   4. Atoms of different elements have different properties
      
   5. Atoms of different elements combine in simple whole-number ratios to produce compounds.
      
   6. Chemical change involves joining, separating, or rearranging
      

   Law of Multiple Proportions - Elements can combine in different ways to form different substances, whose mass ratios are small whole-number multiples of each other.
   

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