Joseph Proust (1754 - 1826)
Current Atomic Model
- He first published his Law of Definite Proportions (or
Law of Constant Composition) in 1794.
- This law states that a compound is composed of exact proportions of elements
by mass regardless of how the compound was created. For example, to make
water there is a specific ratio of grams of hydrogen to grams of oxygen
regardless of where your sample of water was found. All water has this particular
- For example, if one sample of water breaks down into 2 grams of hydrogen
and 16 grams of water, then twice the amount of water would contain 4 grams
of hydrogen and 32 grams of water. The proportion of hydrogen to oxygen
is "definite" or fixed.