Transcript WHAT WE ARE LEARNING 1. WHAT THE ENTIRE UNIVERSE IS MADE OF 2.

WHAT WE ARE LEARNING
1. WHAT THE ENTIRE UNIVERSE IS MADE OF
2. HOW THAT STUFF INTERACTS
(aka, Chemistry)
IN the process of learning that, at no extra charge,
you get to learn…..
A) The people who figured matter out and their discoveries
B) The parts of an atom and their details (and other subatomic
matter - antimatter, dark matter and dark energy if you are interested…)
C) Types of radiation
D) Forces of the Universe
E) The fundamental chemistry laws
F) How to read a periodic table square
G) What’s an Isotope (neutron based) & an Ion (electron based)
OUR UNDERSTANDING OF
CHEMISTRY STARTED WITH
NECESSITIES AND OBSERVATIONS
What a freakin’ pain in the tail….
There must be a better way!
THE BETTER WAY CHEMISTRY!
(Unbalanced Equation)
Ag2S + Al → Ag + Al2S3
Silver sulfide + aluminum
(silver tarnish)
yields
silver + aluminum sulfide
(aluminum tarnish)
EXACTLY HOW SMALL
ARE ATOMS?
THIS STUFF IS TEENY TINY.
Roll film….
http://learn.genetics.utah.edu/co
ntent/begin/cells/scale/
ATOMOS: NOT TO BE CUT
IN the Beginning, we didn’t know jack about
what the universe was made of.
Aristotle
Pliny the Elder: Goats
• use a diet of ivy and crabs thrown up
from the sea to cure themselves of
sickness.
• can see at night just as well as they can
by day, eating goat liver can restore
sight in night-blindness.
• breathe through their ears instead of
their nostrils,
“The blood of a goat • always have a fever; explains why they
are so lively and hotter during mating
will shatter a
• If a goat licks an olive tree the tree will
diamond.”
become barren; a bite kills a tree
All Observation and Reasoning – no experimentation.
IN the Beginning, we didn’t know jack about
what the universe was made of.
“A good decision is
based on knowledge
and not on numbers.”
More Observation and Reasoning – no experimentation.
DEMOCRITUS
This is the Greek
philosopher Democritus,
“the Laughing Philosopher”
because he found the humor
in everything,
He asked: Could matter
be divided into smaller
and smaller pieces
forever?
ATOMOS!
His theory:
Matter could not be divided
into smaller and smaller pieces
forever. There was a “smallest
piece of matter.”
This piece would be
indivisible.
He named the smallest piece
of matter “atomos,” meaning
“not to be cut.”
ATOMOS
To Democritus, atoms
were
small, hard particles
 all made of the same
material
were different shapes and
sizes.
Atoms were infinite in number, always moving and capable
of joining together.
ARISTOTLE AND PLATO
The popular philosophers
of the time, Aristotle and
Plato, had a respected,
(but ultimately wrong)
theory that all matter was
made of combination of
the “four elements,” which
could be divided infinitely.
POPULARITY BEATS GOOD SCIENCE
Atomic Theory was ignored and
forgotten for more than 2000
years!
People are
hilarious.
LAVOISIER AND PROUST
Zee father of Chemistry and
his talented wife.
Law of Conservation of Mass
Law of Definite Proportions
You end with what you started with. H2O is always 2 H’s and 1 O.
Dalton’s Model
In the early 1800s,
the English Chemist
John Dalton
performed a number
of experiments that
eventually led to the
acceptance of the
ATOMIC THEORY.
Dalton’s ATOMIC Theory
He deduced that…
1)all elements are made
of atoms.
(Atoms are indivisible
and indestructible
particles.)
Just a solid ball at this point….
Dalton’s Atomic THeory
Atoms of the
same element are
exactly alike.
Dalton’s atomic Theory
Atoms
cannot be
created or
destroyed
(Law of
Conservation
of Matter)
Atoms combine in specific ways.
Compounds have recipes.)
The recipe for water.
…And his own law,
The Law of Multiple Proportions
You can change the recipe, but you get different stuff,
ATOMIC THEORY .
WHOO HOOOOOOO!!!!!!
This theory became
the
foundation of
modern chemistry.
CROOKES AND HIS
MALTESE CROSS TUBE
Thomson’s Plum Pudding Model
In 1897, the English
scientist J.J.
Thomson used
Crookes’ Tube to
figure out the atom
is made of even
smaller particles.
Cathode Ray Tube
2.2
THOMSON MODEL
Thomson studied
the passage of an
electric current
through a gas.
As the current
passed through the
gas, it gave off rays
of negatively
charged particles.
THOMSON MODEL
This surprised
Thomson, because
the atoms of the gas
were uncharged.
Where had the
negative charges
come from?
Where did
they come
from?
J.J. Thomson: Cathode Rays
1. Cathode rays can be deflected by a magnetic field
and by an electrical field.
2. Cathode rays are negatively charged particles
THUS: There are negative bits in atoms – Electrons.
Thomson concluded that the
negative charges came from within
the atom.
A particle smaller than an atom had
to exist.
The atom was divisible!
Thomson called the negatively
charged “corpuscles,” today known
as electrons.
Since the gas was known to be
neutral, having no charge, he
reasoned that there must be
positively charged particles in
the atom.
But he could never find them.
2.2
Roentgen
Discovered
X–Rays
Used a Crookes (cathode ray) tube in
the dark – the phosphescent screen
across room lit up!
How to Make X-Rays:
1. Shoot electrons (cathode rays) at an atom.
Option A: If you get close to the
nucleus, the electrons slow down.
Losing speed means losing
energy – X-ray energy!
Option B: If you hit another
electron out of it’s orbit, a faster
orbiting electron slows down
(loses energy -X-ray energy!) to
take its place.
The Curies
There are
radioactive rocks in
nature!
Henri Becquerel
You can make things radioactive
by shooting X-rays at them!
RADIOACTIVITY
Three types of radiation were discovered by Ernest
Rutherford:
I am
better
than you.
THE RUTHERFORD
RADIATION EXPERIMENT
Let radiation stream out of a lead block, have it shoot between a
positive and a negative plate, and see which way they go.
– ALPHA particles (positive, charge 2+, mass 7400 times of e-)
– BETA particles (negative, charge 1-)
– GAMMA rays (high energy light)
Rutherford’s Gold Foil Experiment
In 1908, the English physicist Ernest Rutherford
Said, hmmm…wonder what would happen if you smacked an atom
with alpha particles….
More from Ernest Rutherford (1910)
How he figured out there was a positively
charged middle (nucleus)
Scattering experiment: firing alpha particles at a gold foil
THE GOLD FOIL EXPERIMENT
(DISCOVERING THE NUCLEUS)
Some alpha
particles bounced off
the gold foil.
This means the
mass of the atom must
be concentrated in the
center and is positively
charged!
Thompson’s model
could not be correct!
RUTHERFORD’s
CONCLUSION
This could only mean that the gold atoms in the sheet
were mostly open space. Atoms were not a pudding
filled with a positively charged material.
Rutherford concluded that an atom had a small, dense,
positively charged center that repelled his positively
charged “bullets.”
He called the center of the atom the “nucleus”
The nucleus is tiny compared to the atom as a whole.
Rutherford’s MODEL
Rutherford reasoned that
all of an atom’s positively
charged particles were
contained in the nucleus.
The negatively charged
particles were scattered
outside the nucleus around
the atom’s edge.
Chadwick’s Experiment (1932)
H atoms - 1 p; He atoms - 2 p
mass He/mass H should = 2
measured mass He/mass H = 4
a + 9Be
1n
+ 12C + energy
neutron (n) is neutral (charge = 0)
n mass ~ p mass = 1.67 x 10-24 g
2.2
BOHR MODEL
In 1913, the Danish
scientist Niels Bohr
proposed an
improvement. In his
model, he placed each
electron in a specific
energy level.
BOHR MODEL
According to Bohr’s atomic model,
electrons move in definite orbits
around the nucleus, much like planets
circle the sun. These orbits, or energy
levels, are located at certain distances
from the nucleus.
Wave Model
THE WAVE MODEL
Today’s atomic model is based on
the principles of wave mechanics.
According to the theory of wave
mechanics, electrons do not move
about an atom in a definite path, like
the planets around the sun.
THE WAVE MODEL
In fact, it is impossible to determine the exact location
of an electron. The probable location of an electron is
based on how much energy the electron has.
According to the modern atomic model, at atom has a
small positively charged nucleus surrounded by a large
region in which there are enough electrons to make an
atom neutral.
ELECTRON CLOUD:
A space in which electrons are
likely to be found.
Electrons whirl about the
nucleus billions of times in one
second
They are not moving around in
random patterns.
Location of electrons depends
upon how much energy the
electron has.
ELECTRON CLOUD:
Depending on their energy they are locked into a certain
area in the cloud.
Electrons with the lowest energy are found in the
energy level closest to the nucleus
Electrons with the highest energy are found in the
outermost energy levels, farther from the nucleus.
The Whole History In a Simple Table
Solid Electron Nucleus Neutron
Democritu
s
Dalton
Electron Electron
Orbit
Cloud
X
X
Thomson
X
Rutherford
X
X
Chadwick
X
X
X
Bohr
X
X
X
Wave
(Quantum)
X
X
X
X
X
ATOMIC MODELS
This is the Bohr model.
In this model, the nucleus
is orbited by electrons,
which are in different
energy levels.
A model uses familiar ideas to explain
unfamiliar facts observed in nature.
A model can be changed as new information is
collected.
The atom actually looks more like this….
In the very tiny center are protons and neutrons. The
electrons buzz around in the clouds around it.
Measured mass of e(1923 Nobel Prize in Physics)
e- charge = -1.60 x 10-19 C
Thomson’s charge/mass of e- = -1.76 x 108 C/g
e- mass = 9.10 x 10-28 g
2.2