C1 – The Developing Atomic Model
What is our world
made of??
What are mountains made of?
What is water made of?
Thinking about the world…
• Is really hard
Aluminum Foil
1.
2.
3.
4.
Grab a piece of aluminum foil
Tear it in half
Tear it in half again
Repeat until you cannot tear it
anymore
What do you have left?
Balloon
1. Fill a balloon with a scent
2. Fill with air, and tie off end
3. Smell the balloon
Can you smell the scent? How?
Mass of Volleyball
1.
2.
3.
4.
5.
Weigh the volleyball on the scale
Record the mass
Fill with air
Record the mass
Compare the two masses (deflated
vs. inflated)
What can you conclude about the air
that was added to the balloon?
Ice, Water, Steam
1. Turn on the hotplate
2. Place Ice cube onto hotplate
3. Observe the changes of state
Has whatever makes up ice changed
when it becomes water, then again to
steam
Ancient Greek Philosophers
• The ancient Greek
philosophers
wondered why
matter behaves as it
does
• Performed thought
experiments in their
minds
Leucippus 500 BCE
• Was an atomist,
believing the world
consisted of two
fundamental
principles, atoms and
void (empty space)
• These atoms were
indestructible and
existed in infinite
shapes and sizes
Leucippus cont.
• The atoms moved through out the
void bouncing off one another
• Occasionally they became “hooked”
on one another to form cluster
• These clusters of different atoms are
what is responsible for visible matter
Empedocles 450 BCE
• All matter is
composed of the
four ultimate
elements
• Fire
• Air
• Water
• Earth
• Combine to produce
all known structures
Empedocles cont.
• Identified the ultimate
elements as
indestructible and
unchangeable
• Stated nothing new
comes into being: all
changes are attributed
to rearrangement of
element within matter
• Believed to be the
TRUTH for 2000 years
Democritus 400 BCE
• Tiny particles existed
(atomos) that could not
be broken down further
• Material matched the
shape of the atom
• Iron atoms; solid and
strong with hooks to lock
them
• Water atoms; smooth and
slippery
• Air atoms; light and
whirling
Democritus cont.
• Each atom was
visibly different with
regard to shape,
size, and
arrangement
• Connections
between atoms
were explained by
mechanical linkages
• Hook and eyes
• Balls and sockets
Alchemy 500-1600 AD
• First people to
perform
experimentation
• Practiced throughout
the old world by
people who were
part
•
•
•
•
Philosopher
Mystic
Magician
Chemist
Alchemy cont.
1. Attempted to change base metals in gold
• Discovered new elements and properties
by accident
2. Investigated the preparation of the “elixir
of life”
3. Attempted to develop a “universal
solvent”
4. Developed the technique of distillation
Antoine- Laurent de Lavoisier
• Discovered that,
although matter may
change its form or
shape, its mass always
remain the same
• Identified 23 elements;
pure substance that
cannot broken down
into simpler substances
Antoine- Laurent de Lavoisier
cont.
• Element - pure substance that cannot be chemically broken
down into simpler substances
• Identified 23 elements. He based his investigations on careful
measurement and observations of designed experimentation
• How does this differ from alchemy?
• Recognized mixtures exist and identified air as a mixture of
oxygen and some other gas
In a group of 4…
• Try to brainstorm a “model” that explain
what everything around us is made of…
• Some ideas to think about
• How is pure gold different/same than
plastic
• How is ice different/same than water
Atoms
• Smallest particle of any type of matter
• All matter is made of atoms
• Building blocks
• Different atoms exist for each
element
• Gold, Silver, Copper
John Dalton
• English chemist (early 1800)
• Atom is a solid, indivisible,
indestructible sphere
• Atoms are the smallest unit
that exist
• All atoms have similar
characteristics
Dalton’s Billiard Ball Model
Dalton’s “billiard ball” model
1. All elements are composed of atoms. Atoms are
indivisible and indestructible particles
2. Atoms of the same element are exactly alike.
They all have the same mass and chemically
behave the same way
3. Each element is characterized by the mass of its
atoms. Different elements have atoms that
differ in mass and chemical properties from the
atom of every other element. Atoms of
different element are different
1. The joining of atoms of two or more elements
forms compounds
2. Atoms are neither created nor destroyed in a
chemical change
J.J. Thomson
• A British Physicist began experimenting
with a Crookes Tube
• When a magnet was brought nearby the
tube; the beam would move
• He made a significant conclusion…
J.J. Thomson
• Presence of very
light negative
particle called
electrons
• disproved Dalton’s
theory that the
atom was
indivisible
“Plum
Pudding”
Thomson’s “plum pudding” model
1. Electrons have small
mass and a negative
charge
2. An atom is a sphere of
positive electricity
3. Negative electrons are
embedded in the
positive sphere, so that
the resulting atom has a
neutral charge
Earnest Rutherford
• Tested Thomson’s
model using gold
foil and alpha
particle radiation
• Shooting a “laser”
beam through
gold foil to a
detector
• While the majority the laser beam passed
through the gold foil, a small amount was
blocked.
• What conclusion can you draw from his
observation
• Rutherford proposed the presence of a dense
positively charged core called nucleus
Rutherford’s “Nuclear” model
1. Nucleus is a very tiny, dense, and positively
charged core of an atom
2. All of the atom’s positively charged particles,
called protons, are contained in the nucleus
3. The nucleus is surrounded by mostly empty
spaces
4. Rapidly moving, negatively charged electrons
are scattered outside the nucleus around the
atom’s edge in what is referred to as an
electron cloud
Niels Bohr
• Proposed a theory of
the hydrogen atom
(the most simple of
all atoms) consisting
of one heavy proton
in the center with
one lighter electron
in orbit around the
proton
Bohr’s “planetary model”
1. Electron move around the nucleus in
nearly circular paths called orbits
2. Each electron in an orbit has a
definite amount of energy. Electrons
can move within these energy levels
without loss of energy
3. The further the electron is from the
nucleus, the greater it energy
1. Electrons cannot exist between these
orbits, unless energy is added
2. Each orbit is located at a certain
distance from the nucleus
3. Electrons are stable when they are at
lower energy level, closer to the
nucleus
Dalton’s Model
Thompson’s Model
Rutherford’s Model
Bohr Model?
Bohr’s Model
Search for the Atom
History of the
Atomic Model
Quantum Model of the Atom
• Electrons do not move about the atom’s nucleus in a definite
path like planets around the Sun
• It is impossible to determine the exact location of an electron
• The probable location of an electron is based on it energy
• Energy levels are divided into four sublevels, and each
sublevel is made up of several pairs of electrons called orbitals
• The quantum model of the atom show how electrons move
randomly in electron clouds called orbital
Assignment
• Write a short letter pretending to be Thomson, Rutherford, or
Bohr to an earlier scientist explaining how you revised their
atomic model and what you discovered. Give reference to the
experiment that lead to your discovery.
• J.J. Thomson writing to John Dalton
• Earnest Rutherford writing to J.J. Thomson
• Niels Bohr writing to Earnest Rutherford
What are we learning today?
• John Dalton
• Model
• J.J. Thompson
• Model, Experiment
• Earnest Rutherford
• Model, Experiment
• Niels Bohr
• Model
Periodic table of the elements
Atoms & Elements
What do we know about the atom or
any elements?
Atom
• Building blocks of
matter
• Smallest unit of an
element
• properties of the
element
• Electrically neutral
Just How Small is
an Atom?
How Small? Very
Small
Nucleus
• Core of the
atom
• Consists of
• neutrons
• protons
• Mass of an atom
Subatomic particles
• Atom is
composed of
particles that
are smaller than
the atom
• Electron
• Proton
• Neutron
Neutron
• No electrical
charge
• 1 Mass Unit
Proton
• Positive electrical
charge
• 1 Mass Unit
• Each element has
a different number
of protons
Electron
• Negative electrical
charge
• Located in the outer
shell
• Size too small to be
currently measured
• Mass of 1/1837 Mass
Unit
Review
Subatomic
Particle
Symbol and
Charge
Mass
Location
Proton
P+
1 amu
Nucleus
Neutron
N
1 amu
Nucleus
Electron
E-
1/1837 amu
Electron shell
Periodic table of the elements
Overview of the atom
Static Electricity Demo
• Electroscope
• Glass Rod
• Fur