Transcript Ancient Atomic Theory (January 2014)

Learning Goals
 Students will:
1) Understand the improvements to the Atomic Model
through history
2) Understand how each advancement leads to the
present model of the atom.
Success Criteria
 Students will:
1) Record the important facts in an information chart.
2) Understand the advancements of each new atomic
model.
3) Identify the weakness of the model that lead to
further investigation.
Presentation Outline
•Introduction
•Leucippus and Democritus
•Empedocles and Aristotle
•Aristotle and St. Thomas Aquinas and the effect of
the Church
•The Alchemists
Introduction
Atomic theory first originated with Greek philosophers around
2500 years ago. This basic theory remained unchanged until
the 19th century when it first became possible to test the
theory with more sophisticated experiments.
As science has rapidly advanced over the past few centuries
the atomic theory has been refined in accordance with the
accepted scientific principles and theories of the time.
Advances in technology and theory that have allowed
experiments to be designed that enable us to probe matter to
microscopic scales.
Ancient Atomic Theory
The atomic theory of matter was first proposed
by Leucippus, a Greek philosopher who lived at
around 400BC. At this time the Greeks were
trying to understand the way matter is made.
But according to Leucippus, it is possible to
subdivide matter in smaller and smaller parts,
and he proposed that this process can be
continued until eventually you arrive at small
particles which can not be further subdivided.
Leucippus
Leucippus called these indivisible particles
atoms (from the Greek word atomos, meaning
“indivisible”).
Ancient Atomic Theory continued..
Leucippus's atomic theory was further
developed by his disciple, Democritus
Democritus suggested the atomic theory,
explaining that all things are "composed of
minute, invisible, indestructible particles of
pure matter which move about eternally in
infinite empty space“. This was the atom.
Democritus
Problems
 Leucippus and Democritus were on the right track but
they were PHILOSOPHERS
 NOT OF THESE THEORIES WERE EVER TESTED
EXPERIMENTALLY
 Given the simple technology – it was difficult to test
these theories
Ancient Atomic Theory continued..
According to the ancient Greeks,
atoms were all made of the same
basic material, but atoms of different
elements had different sizes and
shapes.
The sizes, shapes, and arrangements
of a material’s atoms determined the
material’s properties.
Another Greek Philosopher, Empedocles,
proposed the 4-element theory of matter –
in which all matter was seen to consist of
Air, Fire, Water and Earth.
Aristotle
 Around 340 B.C. Aristotle said he didn't
believe in the theory of Atoms because you
would be putting a restriction on the gods.
 If the gods wanted to divide an element to
something smaller than an atom, they
could. The concept that God or gods had
unlimited power was quite popular.
 In addition Aristotle introduced the fifth
element (ether) that he said all heavenly
bodies (Sun, moon, and stars, etc.) were
made of. Hence ether was a heavenly
material
St. Thomas Aquinas
 Aquinas was one the great philosophers of
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the Catholic Church.
He used logic to prove the existence of God
and used the teachings of Aristotle as a
basis for his thinking.
As a result the Catholic Church followed
Aristotle’s 5-element theory.
Since it was considered blasphemy to
question the teachings of the church, most
people (including scientists) did not
question the 5-element theory.
As a result, Aristotle’s the 5-element theory
existed for over 2000 years.
Modern Astronomy vs. The Church
 Famous Astronomers Galileo and
Copernicus believed that the Sun
was in the middle of the solar
system and not the Earth.
 This conclusion was based on many
years of careful data collection by
many scientists, yet the Church was
convinced that God placed man at
the center of the universe.
 Galileo was forced to recant his
theory and his life was spared but he
was placed under house arrest for
the rest of his life.
Alchemy
 Alchemists were a combination of scientist, wizard,
medicine man and philosopher. They believed in the 5element theory of matter and made some developments to
Science in the Middle Ages (1000 – 1500).
 Alchemists also made many biased, incorrect conclusions
based on poor scientific reasoning.
 Since Aristotle believed that the fifth element could turn
cheap metals into gold and cure disease and old age. Many
alchemists pursued the discovery of the 5th element.
Alchemists
An alchemist conducting
experiments with his elves
An alchemist expelling demons
Changes in Scientific Thinking
Alchemists do take the credit
for developing many types of
glassware used today in
Chemistry, as well as many
experimental processes. BUT
they made few scientific
advances.
 Modern science did not begin until scientists:
Began using careful experimental techniques to make
observations
2. Made conclusions based on these experiments with no biases.
1.
This led many early scientists into trouble from the Church.
The Modern Atomic Theory
For centuries scientists did not have the methods or
technology to test their theories about the basic
structure of matter, so people accepted the ancient
Greek view.
In the 19th century John Dalton made
inferences that exhibited how atoms
bond together in definite proportions.
Dalton was able to say that atoms of
different elements combine in
whole number ratios.
John Dalton