Download Defining the Atom

Chemistry 4.1
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4.1
Defining the Atom
The lab technician shown
here is using a magnifying
lens to examine a bacterial
culture in a petri dish. When
scientists cannot see the
details of what they study,
they try to obtain
experimental data that help
fill in the picture.
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4.1
Defining the Atom
> Early Models of the Atom
Early Models of the Atom
• An atom is the smallest particle of an element
that retains its identity in a chemical reaction.
• Philosophers and scientists have proposed
many ideas on the structure of atoms.
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4.1
Defining the Atom
> Early Models of the Atom
Democritus’s Atomic Philosophy
How did Democritus describe atoms?
Democritus
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4.1
Defining the Atom
> Early Models of the Atom
Democritus believed that atoms were
indivisible and indestructible.
Democritus’s ideas were limited because
they didn’t explain chemical behavior and
they lacked experimental support.
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Defining the Atom
> Democritus cont…….
Democritus coined the word “atomos”
His Model of the Atom was a round
Circle.
O
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4.1
Defining the Atom
> Early Models of the Atom
Dalton’s Atomic Theory
How did John Dalton further
Democritus’s ideas on atoms?
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Defining the Atom
> Democritus Ideas
Ideas:
Matter is composed of empty space
through which atoms move.
Atoms are solid, homgeneous,
indestructible and indivisible.
Different kinds of atoms have different
sizes and shapes.
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Defining the Atom
> Question!
If atoms are primarily composed space
why can’t we pass our hand through a
solid object?
Ans: atoms in a object are bonded
together with electrical forces. These
bonds are not easily broken.
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Defining the Atom
>
The differing peoperties of matter are
due to the sizes, shape, and movement
of atoms.
Apparent changes in matter result from
changes in the grouping s of atoms and
not from changes in the atoms
themselves
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4.1
Defining the Atom
> Early Models of the Atom
By using experimental methods, Dalton
transformed Democritus’s ideas on atoms
into a scientific theory.
The result was Dalton’s atomic theory.
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4.1
Defining the Atom
> Early Models of the Atom
All elements are composed of tiny indivisible
particles called atoms.
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4.1
Defining the Atom
> Early Models of the Atom
Atoms of the same element are identical. The
atoms of any one element are different from
those of any other element.
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4.1
Defining the Atom
> Early Models of the Atom
Atoms of different elements can physically mix
together or can chemically combine in simple
whole-number ratios to form compounds.
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4.1
Defining the Atom
> Early Models of the Atom
Chemical reactions occur when atoms are
separated, joined, or rearranged. Atoms of one
element are never changed into atoms of
another element in a chemical reaction.
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Defining the Atom
> Dalton’s model of the atom.
Daltons model of the atom was the same
as Democritus. He just validated
Democritus’s thoughts
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4.1
Defining the Atom
> Sizing up the Atom
Sizing up the Atom
What instruments are used to observe
individual atoms?
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4.1
Defining the Atom
> Sizing up the Atom
Despite their small size, individual atoms
are observable with instruments such as
scanning tunneling microscopes.
The radius of most atoms fall within
a range of 5 X 10 -11m to 2 X 10 -10m
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4.1
Defining the Atom
> Sizing up the Atom
Iron Atoms Seen Through a Scanning
Tunneling Microscope Size 7.13 X 10-9 m
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4.1 Section Quiz
Assess students’ understanding
of the concepts in Section 4.1.
Continue to:
-or-
Launch:
Section Quiz
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4.1 Section Quiz
1. The ancient Greek philosopher credited with
suggesting all matter is made of indivisible
atoms is
a. Plato.
b. Aristotle.
c. Democritus.
d. Socrates.
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4.1 Section Quiz
2. Dalton's atomic theory improved earlier
atomic theory by
a. teaching that all matter is composed of tiny
particles called atoms.
b. theorizing that all atoms of the same
element are identical.
c. using experimental methods to establish a
scientific theory.
d. not relating atoms to chemical change.
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4.1 Section Quiz
3. Individual atoms are observable with
a. the naked eye.
b. a magnifying glass.
c. a light microscope.
d. a scanning tunneling microscope.
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