[Under Construction]



Early Models of the Atom:


    1.    Define the term atom.

    2.    List the postulates of Dalton's atomic theory.

Key Terms:

    atom    law of constant position    atomic theory of matter

Web Resources:

    www.chem.ucr.edu/faculty/ bartels/chemcont_.gif



Atoms are the smallest particle of an element retaining all of its properties.  Though, invisible to the eye and microscope (limited images are possible with the tunneling microscope), you could theorize that an atom of gold would have the same luster and texture (look and feel) as a solid gold bar.  The belief in atoms as the basic building block of matter dates back o the Greek philosophers (450 BC) when Democritus first proposed the existence of atomos (small particles of matter).  Unfortunately Democritus' views were not accepted until the early 1700s.

1700 - Lavoisier - The Law of Conservation of matter - Matter can not be created nor destroyed.
1799 - Proust - Law of Constant Composition - Given compounds always contain the same proportion of elements.
1803 - Dalton - Atomic Theory of Matter
    Elements are composed of atoms
    Atoms in an element are identical but different from other elements
    Atoms cannot be destroyed or created by physical or chemical reactions
    A give compound always has the same ratios and kinds of atoms

As stated in the previous chapter, there are around 100 naturally occurring elements.  Like the letters in the alphabet, these atoms arrange in different configurations to build all the matter in our atmosphere. (We cannot be sure outside of this.  We've never been there.)  



Last modified: September 13, 2002