Transcript 1.atomictheory

Atomic Theory 1
What Happens in Vegas stays in Vegas
Atomic Theory
Theories in science are proposed to explain the evidence available at the time.
As new evidence is discovered theories are adapted to explain new data.
This is the nature of Science.
In the future this will continue.
Plato
Democritus
460-370 BC
Atoms make up the world
Plato
Teacher of Aristotle
Aristotle
384-322 BC
Four Elements
Forces
Properties
The Four Element Theory
Aristotle harmony
wetness
conflict
Water
Wind
coldness
hotness
Earth
Fire
dryness
The Four Element Theory lasted for about 2 thousand years because no
one tested the theory with scientific experiments.
It was not a scientific theory- which is tested by experiment.
John Dalton
1766-1844
Atomic Theory
Dalton’s Atomic Theory- 1808
Evidence
1.
The Law of Conservation of Mass
2.
The Law of Constant Composition- water is 11 % H
and 89 % O
Theory
1.
Each atom is an indestructible and unique spherical
particle
2.
Atoms combine in simple whole number ratios to
form compounds
Hydrogen
Oxygen
Lithium
Dalton Theory- Water
1gH
1gH
16 g O
18g O
Dalton Theory- Water
16 g O
1gH
1gH
18g O
Dalton Theory- Water
16 g O
1gH
2 gH
x
18 g H2O
1gH
100%
=
11% H
89 % O
Having a molecule (atoms
combine in simple whole # ratios)
explains the law of constant
composition.
Still
11 % H
89 % O
No matter how much water you have its still 11% H
2H2
+ O2

2H2O
If the atoms are not destroyed then the mass does not change
J. J. Thomson 1871-1937
The Thomson Theory of the Atom
Evidence
1.
The electrical nature of matter
beta particles
static electricity
current electricity
Theory
1.
The atom is made up of positive material with
negative particles throughout- like blueberries in a
blueberry muffin.
The Thomson Atom 1903
+
+
+
-
-
+ +
+
+
+
- +
+
+
- +
+
+ + +
+
+ +
-
Ernest Rutherford 1871-1937
The Rutherford Atom 1911
Simulation
Evidence: Gold Foil Experiment
1.
99.99 % of alphas are not deflected
2.
0.01 % of alphas are radically deflected
Theory
1.
Most of the atom is empty space.
2.
There is a small dense nucleus in the center of the
atom that makes up most of the mass. Electrons
circle the nucleus randomly.
The Rutherford Atom 1911
Scale: nucleus is home plate; atom is the baseball field
Be
Nucleus- is small but has most of the mass
Nucleus- 4 protons and 5 neutrons
-
-
Electrons
Cornelis Escher 1898-1972
Discovery of the Nucleus
Size of the Atom