Chem+A+Group+1

=**__Dalton's Atomic Theory__** (1803-1808)=

=
Some general background on John Dalton:  =====


 * he was a school teacher and a meteorologist
 * after Lavoisier observed that matter is never created or destroyed, Dalton began thought that matter also had to be made up of small indivisible particles
 * he also developed an Atomic Theory,a combination of past knowledge and his own contributions, for which he is most famous for:

media type="custom" key="2091843"

[|John Dalton] [|A picture of Dalton]

__**Dalton's Theory**__
 * 1) **All elements are composed of tiny, indivisble, particles called atoms.**
 * 2) **Atoms of the same element are identical but differ from the atoms of any other element.**
 * 3) **Atoms of different elements can physically mix together or can chemically combine with one another. They chemically combine in fixed, small whole number ratios. (example: H2O has a 2:1 ratio and Fe2O3 has a ratio of 2:3)**
 * 4) **Chemical reactions occur when atoms are separated, joined or rearranged. Atoms of one element are never changed into another.**

media type="google" key="8508037603850657912&hl=en&fs=true" width="400" height="326" An explanation of John Dalton's Atomic Theory and the events preceding it's creation.

Leading Up to The Atomic Theory

 * In the 1780's, Lavoiser made **careful quantitative measurements**. Now, compositions of compounds could be determined with accuracy.
 * In 1799, Proust established the **Law of Constant Composition**, also known as the Law of Definite Proportions.
 * Both these findings assisted Dalton in proposing the Law of Simple Proportions in 1803.
 * In the early 1800s, Dalton formulated his **atomic theory** in an attempt to explain how and why elements would combine with one another in fixed ratios.

**INTERESTING FACT!**

 * Since Dalton proposed the Atomic Theory, there have been many modifications to it. Those modifications include the divisibility, destruction, radioactive decay, isotopes of atoms and diatomicity of gases.

Chemistry Involved

 * Dalton came upon the idea that chemical combination consists in the interaction of atoms of definite and characteristic weight.
 * Dalton stated, "The elements of oxygen may combine with a certain portion of nitrous gas or with twice that portion, but with no intermediate quantity."
 * Dalton thought that whole number ratios can be used to represent the structures of compounds.
 * Dalton performed experiments with different gases during the turn of the 19th century, which lead to the development of his atomic theory

[|Experiments with Gases]

**Importance**

 * If Dalton did not propose the Atomic Theory, then we would have never invented the atomic bombs, atomic weapons, and much more.

What else was going on in chemistry?

 * advances were being made by Fredrich Wöhler in organic chemistry
 * earlier in Dalton's life, around 1770, the discovery of oxygen and the chemical revolution took place
 * combustion and the theory of phlogistan were being explored during this time