Download The Atom - Williamstown Independent Schools

The Atom:
From Philosophical Idea to Scientific
Theory
Particle Theory of Matter


Dates back to 400 B.C. and Greek
philosophers like Democritus
Coined the term “atom” which
meant “indivisible”
Experiments Advance

In the 18th century several basic
scientific laws develop.
Law of Conservation of Mass

Mass is neither created nor
destroyed during normal chemical
reactions.
Law of Definite Proportions

A chemical compound contains the
same elements in the same
proportions regardless of sample
size or source.
Law of Multiple Proportions

If two or more different compounds
are composed of the same two
elements then ratios of the masses
of the second element combined
with a certain mass of the first
element is always a ratio of small
whole numbers.
John Dalton
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In 1808 an English schoolteacher
proposed an explanation for the 3
basic laws.
This became known as the Atomic
Theory
Dalton’s Atomic Theory


All matter is composed of particles
called atoms
Atoms of a given element are
identical in size, mass and other
properties. Atoms of different
elements differ in size, mass and
other properties.
Dalton’s Atomic Theory


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Atoms cannot be subdivided,
created or destroyed
Atoms of different elements
combine in simple, whole number
ratios to form chemical compounds.
In chemical reactions, atoms are
combined, separated or rearranged.
Modern Atomic Theory

As technology improved and more
information became available
Dalton’s theory has become
modified.
Modern Atomic Theory

Two basic tenets remain:


All matter is composed of atoms
Atoms of one element differ in
properties from atoms of another
element.
Assignment
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
Read pages 65-68
Answer the following:



Name the various compounds that the
carbon atom was a component of in
Levi’s story.
Why was it unlikely for the carbon atom
to have been taken into the bird’s
bloodstream?
Section Review pg. 69 (1-3)