Download Development of the Atomic Theory

Development
of the Atomic
Theory
From Democritus to Dalton
Democritus
 Greek
philosopher
 400 BC
 All matter is made
up of atoms
 Atoms are solid
and indestructible
 Atomos =
‘indivisible’
 No experiments to
support idea
The Atom
 The
smallest
particle of an
element that
retains the
properties of
that element
 Basic building
block of matter
Learning Check #1
1.
2.
3.
What does the
word indivisible
mean?
What is an
atom?
Who first
proposed the
idea of atoms?
1.
2.
3.
Cannot be
split!
The smallest
particle of an
element that
retains the
properties of
that element
Democritus
Antoine Laviosier (1774)



Developed the Law
of Conservation of
Mass
Matter, like energy, is
neither created nor
destroyed in an
ordinary chemical
reaction
“One may take it for
granted that in every
reaction there is an
equal quantity of
matter before and
after.”
Joseph Proust
 Developed
Law of
Definite Proportions
 Any given
compound always
contains the same
elements in the
same proportions
by mass.
 Example – Water is
always 88.9%
oxygen and 11.1%
hydrogen by mass
Learning Check #2
1.
2.
3.
In a chemical
reaction if I start
with 100 g of
material, how many
grams should be
there at the end?
In a compound,
what do we know
about the
proportions of
elements?
Who developed
the Law of
Conservation of
Mass?
1.
2.
3.
100 g
Always the same!
Antoine Lavoisier
John Dalton (1803)
 English
school
teacher
 Developed the first
atomic theory.
 First attempt, using
experimentation, to
prove the
existence of atoms
and explain the
structure of matter
Four Parts of Atomic Theory
1.
All matter is composed of indivisible
atoms.
2.
All atoms of the same element are
identical but are different from atoms of
other elements.
3.
A chemical compound always contains the
same atoms in the same ratio.
4.
In chemical reactions, atoms from one or
more compounds or elements rearrange to
form one or more new compounds. New
elements are not formed.
Learning Check #3
1.
2.
3.
According to
Dalton, all matter is
made up of?
Are all atoms of
silver the same?
What part of
Dalton’s theory
supports your
answer?
Are new elements
formed in a
chemical reaction?
1.
2.
3.
Indivisible atoms
Yes. Part #2.
No.
The Law of Multiple Proportions
 Dalton
could not use his theory to
determine the elemental compositions of
chemical compounds because he had
no reliable scale of atomic masses.
 Dalton’s
data led to a general statement
known as the law of multiple proportions.
 Law
states when two elements combine
to form more than one compound, the
mass ratio for one element is small whole
numbers.
What does this mean?
 For
example:
 1.00-g of N will combine with 1.14g of O to form NO.
 Also, 1.00-g of N will combine with
2.28-g of O to form NO2.
 The ratio of the O masses, 1.14 to
2.28, is a 1:2 ratio.