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Atomic Theory Timeline
Transcript of Atomic Theory Timeline
The first theory of the atom was proposed by _1_ around 430 B.C. However it was __2__ who proposed the first Atomic Theory. He said all matter is made up of tiny indivisible and indestructible atoms. Also, __3__ of the same element are the same. Third, atoms of different elements are different. And finally, atoms combine in ___4__ to form compounds. Dalton based his theory on the work of Lavoisier (Law of ___5___) and Proust (Law of Definite __6__).The discovery of the three atomic particles (_____7_________) led to the first revision of Dalton’s atomic theory. It was revised for a second time when isotopes were discovered, and it was determined that atoms of the same element are not identical, and may have different numbers of electrons. Ernest Rutherford conducted the ___8__ experiment which determined that the atom is mostly __9__, with a very small, positive __10__.
Importance Of These Discoveries
These ideas and discoveries are important for later scientific endeavors because we can refer back to them and learn from our mistakes. We can use them to see what we do and don’t know which can give us ideas on how to find new information. They could also be used as research for current experiments. These ideas are also the basis of all our knowledge of atoms and subatomic particles.
proposed first idea of the atom:
substances made up of tiny indestructible, indivisible particles called "atomos."
He gave the explanation for the three previously mentioned laws
proposed first Atomic Theory
1) All matter is composed of indivisible atoms
2) All atoms of a given element are identical in mass and all other properties
3) Different elements have different atoms; for example, some atoms have different masses
4) Atoms are indestructible and retain their identities in chemical reactions
5) Chemical reactions involve the combination, separation, and rearrangement of atoms
He proved his ideas with scientific evidence and experimentation so he was the first to have a
Law of Conservation of Mass:
matter cannot be created or destroyed, only rearranged
Law of Combining Volumes:
at constant temperature and pressure, volumes of reacting gases and gaseous products are in the ratio of small whole numbers
equal volumes of gases, under the same conditions have the same number of particles (6.02x10^23)
discovered that uranium ores emit radiation resembling X-Rays and that it exposed film
used cathode rays to discover the electron
Later, the cathode ray was used to discover the
he disproved Dalton--atoms are divisible
Plum Pudding Model
energy is not emitted constantly, but in small packets called quantum
used X-Ray experiments to discover the atomic number of an element
if waves can behave like particles, then particles can behave like waves
Schrodinger's Wave Equation
-treat the electron like a wave
-developed an equation used to determine the probability of finding the electron in any given place around the nucleus
-solutions to the equation are quantum numbers
Heinsenberg's Uncertainty Principle:
it's impossible to know both position and velocity of an electron at the same time
discovered the neutron
He knew the approximate sizes of electrons and protons. He discovered that those masses did not equal the total mass of an atom. He concluded that there must ba a noncharged (neutral) particle making up the rest of the atom
conducted gold foil experiment: He bombarded gold foil with alpha particles. He shot particles (atoms) through foil. Most particles passed through the foil but some were deflected. He concluded that the atom is mostly empty space, with a very small positive nucleus core
Rutherford came up with Nuclear Model
improved upon the atomic model by trying to answer the question: why aren't electrons pulled into the nucleus?
electrons travel in definite energy levels without radiating energy
electrons in each orbit have a certain amount of energy
energy increases as distance from nucleus increases
electrons lose energy by dropping energy levels
According to an article published in The Seattle Times in July of 2010, European physicists made a discovery that could change everything about atomic structure. Researchers discovered new measurements, which show the radius of the proton is actually four percent smaller than what it was previously thought to be. If this is true, then the standard model of the atom would be deemed incorrect. This would be a huge problem, and would mean we know a whole lot less about atoms than we thought. The consequences of such a drastic change could be revolutionary.
The Seattle Times
Article-"Discovery Shakes Up Standard View Of Atomic Structure"
One recent societal issue about the atom is whether or not to use the atomic bomb to seal off the oil spill in the Gulf of Mexico. I can see both the pros and cons to this idea. It would be the perfect solution because the extreme heat generated by the explosion might seal off the oil well. But then there is the overwhelming chance that it wouldn't work. The only tests on this theory that have been done have all been on land and none of them involved oil. Therefore I do not agree with this idea, because it is not likely to be successful, and could end up causing much worse problems. Had scientists tried to go through with this idea, then it would definitely have impacted science and society, because future oil spills would not be as much of a problem if we had a definite solution. However the idea was deemed too dangerous, and wasn't tested, and therefore did not impact science or society.
The New York Times
"Nuclear Option on Gulf Oil Spill? No Way, U.S. Says"
June 2, 2010
atomos means "indivisible" in Greek
so, whatever you have in the beginning is still there in the end
soon after Democritus
did not believe in atoms, believed matter was continuous
was trusted over Democritus for 2000 yrs
This is how Dalton thought the atom would look. Notice the absence of subatomic particles
gas laws (next semester)
Today we know that:
Elements are composed of extremely small particles called atoms. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of one element are different from the atoms of all other elements.
In a cathode ray tube, atoms were shot through a magnetic field and deflected based on whether the particles were positive or negative
(1908 Nobel Prize in Chemistry)
particle velocity ~ 1.4 x 107 m/s
(~5% speed of light)
atoms positive charge is concentrated in the nucleus
proton (p) has opposite (+) charge of electron (-)
mass of p is 1840 x mass of e- (1.67 x 10-24 g)
Rutherford’s Model of
Atoms are very small; they are building blocks of matter.
Atom = smallest particle of an element that retains its characteristics
Cells are different than atoms because they are living.
Cells are actually made of atoms
Each element has a unique number of protons in its nucleus
Number of protons in the nucleus of an atom is called the atomic number
the elements are arranged on the Periodic Table in order of their atomic numbers
Each element has a unique name and symbol
symbol either one or two letters
one capital letter or one capital letter + one lower case
Atoms are composed of three particles - protons, neutrons and electrons
The nucleus contains protons and neutrons
The electrons move outside the nucleus
Neutral atom has same # protons and electrons.
The Modern Atom
The Nuclear Atom:
How did we get there?
Still not quite right
How are things solid?
This looks alot more like the modern atomic model!
Open Note quiz
Atom contains a tiny dense center called the nucleus
The nucleus has essentially the entire mass of the atom
the electrons weigh so little they give practically no mass to the atom
The nucleus is positively charged
the amount of positive charge balances the negative charge of the electrons
The electrons move around in the empty space of the atom
Warm up 10 -12:
Be in your seat at the bell or you are tardy
get your journal
turn in HOT, you have 2 min after the bell
be ready to continue notes- have notebook open and something to write with
Clear off everything else
Review: who are the scientist we have discussed?
what were they trying to find out? Why were they limited in their discoveries?
Title your blank paper "atomic theory demonstrations"
Part one will be called "match in a jar"
write this on your paper and underline it
put on goggles.
hold the jar upside down
light a match and put the flame under the jar
blow it out before you burn yourself
leave goggles on
make observations. (write "observations" under the title for part one and writie what you see as the match burns and after it is gone.
feel the inside of the jar. Write down what you feel
write the question and answer to the following:
how did democritus use observations like this?
what would lead him to believe in atoms in this experiment?
you will now get a balloon, blow it up and tie it off.
label part 2 on your lab paper "balloon electricity"
rub the balloon on your head and then pull away.
on your lab paper write your observation in complete sentences
now lay the aluminum can on its side on the lab table.
rub your hair again and slowly place the balloon by the can.
record observations in complete sentences
Write this on your lab paper and then turn it in:
Nothing in early models explains how one object can exert a force on another object without touching it. These interactions, since discovered in the 1700s have let to alterations of model of the atom. This is when scientists proposed that there were two kinds of charges in the world, positive and negative. They said positive and negative forces attract, but p-p and n-n repel. Normal atoms have an equal number of positive and negative forces, so they do not exert forces on one another.
Continuing on the lab paper i handed out,write "circuit activity" for part three and underline it
you will need to write down every item we try and what happens each time.
Write the following, fill in the blanks and underline the word you put in the blank
a lightbulb works because _____ flow through the circuit delivering ____. If it doesn't light, we can conclude that something is stopping the flow. We saw today that only _____ work. _____ do not. Metals are good_____, so at least some of the_____ in metals are free to move about. Electrons in _____ are not as free, so they are good _____.
Part 4 Electrons as waves - the slinky
we are pretending the student is the electron and the slinky is the electromagnetic wave
oscillate- the movement of an electron up and down or side to side
frequency- how fast an electron oscillates
standing waves- the waves the slinky makes at the correct frequency
when the oscillations increase the energy output by the electron and the frequency _______________
if you change the situation (where the electron is) the _________ of the wave also changes
electrons are like waves and are in energy levels
each energy level produces a specific energy because the electrons have a specific oscillation in that level
When atoms absorb or emit light, the electrons change energy levels, changing the frequencies. Every frequency of light has its own color, so the atoms will emit a different color light.
Each particular element has its own number of electrons in each energy level, so each element produces a different frequency.
This helps explain how Bohr found his model. He used the light emitted to see that there were different combinations of electrons in there energy levels that make up each of the different elements
fast oscilations/ short wavelength
h= plank's constant(6.626 x 10^-34 j.sec
plank said you can determine the energy change between energy levels with this equation