the history of the atom……. democritus was the first to theorize that all matter was composed of...
TRANSCRIPT
The History of the Atom…….The History of the Atom…….
Democritus was the first Democritus was the first to theorize that all to theorize that all matter was composed of matter was composed of atoms!atoms!
The name atom comes The name atom comes from his Greek word, from his Greek word, “atomos”, which means “atomos”, which means not dividable or whole!not dividable or whole!
Democritus’ ideas were Democritus’ ideas were crushed by a another crushed by a another Greek Philosopher, Greek Philosopher, named……….named……….
………………………………Aristotle!!!!Aristotle!!!!
Aristotle asked Aristotle asked Democritus three Democritus three questions:questions:
If we are made of atoms, If we are made of atoms, what holds us together?what holds us together?
Why can’t we see these Why can’t we see these atoms?atoms?
Why don’t we fall down Why don’t we fall down like a bag of marbles?like a bag of marbles?
Democritus was unable to Democritus was unable to answer these questions…….answer these questions…….
And so, people And so, people continued to think continued to think that matter was that matter was continuous - your continuous - your body, the world body, the world around us was one around us was one continuous piece….continuous piece….
This philosophy This philosophy continued for continued for centuries…….centuries…….
During the middle ages, science During the middle ages, science was lost to the world……was lost to the world……
• The only science that was The only science that was done was performed by done was performed by Arabs (Moors) out of Africa Arabs (Moors) out of Africa that conquered Spain!that conquered Spain!
• They traveled from the They traveled from the Middle East to Western Middle East to Western Europe, carrying the great Europe, carrying the great library of Alexandria with library of Alexandria with them!them!
• While the plague and the While the plague and the dark ages were killing dark ages were killing millions, they had………..millions, they had………..
EVERYTHING…..!EVERYTHING…..!
Running water…..Running water….. Dentistry…..Dentistry….. Reading, Writing, Reading, Writing,
Geometry, Geometry, Calculus…Calculus…
Breweries…….Breweries……. Complex gardens Complex gardens
and Agriculture…..and Agriculture…..
Science did not start up again until the Science did not start up again until the Church was challenged….Church was challenged….
The church was preventing The church was preventing people from coming up people from coming up with new ideas and doing with new ideas and doing science!science!
Who were some people that Who were some people that challenged the Church?challenged the Church?
Once the Church is Once the Church is challenged by thinkers, challenged by thinkers, science experiments start to science experiments start to be done!be done!
With independence, came With independence, came independent thought and independent thought and ideas…..ideas…..
During the 1700’s and During the 1700’s and 1800’s….1800’s….
Scientists were discovering Scientists were discovering concepts and relationshipsconcepts and relationships
Scientists were doing large, Scientists were doing large, observable, basic experimentsobservable, basic experiments
They weren’t doing tests with They weren’t doing tests with microscopes or computers!microscopes or computers!
They were doing experiments They were doing experiments with stoves, pots, ovens, and with stoves, pots, ovens, and basic glassware!basic glassware!
With observable properties With observable properties came explanations!came explanations!
Joseph Priestley…….Joseph Priestley…….
Prepared pure Prepared pure OxygenOxygen
Decomposed Decomposed mercuric oxide into mercuric oxide into mercury and oxygenmercury and oxygen
Invented soda popInvented soda pop Discovered carbon Discovered carbon
dioxide and nitrous dioxide and nitrous oxide (laughing gas)oxide (laughing gas)
Priestley noticed that the gas produced Priestley noticed that the gas produced by heating mercuric oxide burned a by heating mercuric oxide burned a candle brightly….candle brightly…. He called the air, “perfect He called the air, “perfect
air”, or “dephlogisticated air”, or “dephlogisticated air”air”
People thought that People thought that phlogiston was a substance phlogiston was a substance that was in materialsthat was in materials
When substances burned, When substances burned, they released phlogiston, they released phlogiston, which eventually caused which eventually caused flames to go out.flames to go out.
Is this true….?Is this true….? He had actually discovered He had actually discovered
oxygen, but didn’t realize it!oxygen, but didn’t realize it!
Antoine Lavoisier…..Antoine Lavoisier…..
Lived during the Lived during the French RevolutionFrench Revolution
Was a brilliant Was a brilliant scientist, but a tax scientist, but a tax collectorcollector
Had his head Had his head chopped off during chopped off during the revolution with the revolution with royaltyroyalty
Lavoisier Proved…..
That substances did not That substances did not give off phlogiston, but give off phlogiston, but used oxygen!used oxygen!
He burned metals in the He burned metals in the air, and weighed them air, and weighed them before and afterbefore and after
The substances weighed The substances weighed more after, because they more after, because they were combining with were combining with oxygen, not giving off oxygen, not giving off phlogiston!phlogiston!
By weighing the materials By weighing the materials before and after…..before and after….. Lavoisier came up with……..Lavoisier came up with……..
The law of Conservation of MassThe law of Conservation of Mass This states:This states:
- Matter cannot be created or destroyed - Matter cannot be created or destroyed in a chemical reaction, simply converted from in a chemical reaction, simply converted from one form into anotherone form into another
The extra mass came from the oxygen in the The extra mass came from the oxygen in the air, which he later measured by reheating the air, which he later measured by reheating the compound formedcompound formed
Joseph Proust…..Joseph Proust….. Examined copper carbonateExamined copper carbonate No matter the amount, No matter the amount,
whenever decomposed it whenever decomposed it would yield 5.3 parts would yield 5.3 parts copper, 4.0 parts oxygen copper, 4.0 parts oxygen and 1.0 parts carbonand 1.0 parts carbon
Came up with the law of Came up with the law of definite compositiondefinite composition
All substances are All substances are composed of definite composed of definite amounts of each element, no amounts of each element, no matter how much or how matter how much or how little of the matter there is!little of the matter there is!
This compound is This compound is always 5.3 parts Cu, always 5.3 parts Cu, 4.0 parts O, and 1.0 4.0 parts O, and 1.0 parts C!parts C!
John Dalton……John Dalton……
A schoolteacher!A schoolteacher! Devised the Law of Devised the Law of
Multiple ProportionsMultiple Proportions Stated that when two Stated that when two
elements form more elements form more than one compound, than one compound, they come together in they come together in whole number whole number ratios……ratios……
WHAT DOES THAT WHAT DOES THAT MEAN…?MEAN…? Carbon and Oxygen form Carbon and Oxygen form
two compounds: two compounds: Carbon dioxide - CCarbon dioxide - C11OO22
Carbon monoxide - CCarbon monoxide - C11OO11
In carbon dioxide, CIn carbon dioxide, C11OO22, , carbon and oxygen carbon and oxygen combine in a 3 parts to 8 combine in a 3 parts to 8 parts mass ratio parts mass ratio
In carbon monoxide, CIn carbon monoxide, C11OO11, , they do so in a 3 parts to 4 they do so in a 3 parts to 4 parts mass ratio…..parts mass ratio…..
Seem obvious….?Seem obvious….?
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IT WASN’T……IT WASN’T……
Scientists didn’t know Scientists didn’t know what was making what was making things come together things come together to react! to react!
In fact, They didn’t In fact, They didn’t even know that atoms even know that atoms existed!existed!
If compounds come If compounds come together in ratios, they together in ratios, they must be made of must be made of smaller pieces!smaller pieces!
John Dalton theorized that John Dalton theorized that these substances were made of these substances were made of atoms!atoms! This led to……….This led to……….
THE ATOMIC THEORY OF MATTER!THE ATOMIC THEORY OF MATTER! All elements are made of tiny, solid, indestructible particles All elements are made of tiny, solid, indestructible particles
known as atomsknown as atoms All atoms of a given element are the sameAll atoms of a given element are the same Atoms of different elements are differentAtoms of different elements are different Atoms of different elements form compounds in whole Atoms of different elements form compounds in whole
number ratios - 1 atom: 1atom, 1 atom: 2 atoms, etc. number ratios - 1 atom: 1atom, 1 atom: 2 atoms, etc. A chemical reaction does not change the atoms themselves, A chemical reaction does not change the atoms themselves,
only how they are combined to form compoundsonly how they are combined to form compounds
BrBr
HH
IIFeFe SS
It took almost 2000 years before It took almost 2000 years before the idea of the atom came back!the idea of the atom came back! John Dalton brought John Dalton brought
Democritus’ idea back!Democritus’ idea back! It seems simple, but It seems simple, but
people did not believe people did not believe that matter was made of that matter was made of little marble-like little marble-like structures called atoms!structures called atoms!
John Dalton’s theory was John Dalton’s theory was wrong in one wrong in one respect……..respect……..
Atoms are not solid and Atoms are not solid and indestructible like marbles…..indestructible like marbles…..
They contain different They contain different parts…….parts…….
However, scientists did However, scientists did not know this until parts not know this until parts of the atom were of the atom were discovered…..discovered…..
What part of the atom What part of the atom do you think was do you think was discovered first…..?discovered first…..?
THE ELECTRON…!
Why do you think it Why do you think it was the first part of was the first part of the atom to be the atom to be discovered…..?discovered…..?
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The electron is on the outside of the The electron is on the outside of the atom!atom!
The electron is the ONLY part of the The electron is the ONLY part of the atom that can be added or removed to atom that can be added or removed to an atom!an atom!
The electron is tiny and light, and that The electron is tiny and light, and that is why it can be added or removed!is why it can be added or removed!
This is what we call electricity…This is what we call electricity…moving electrons!moving electrons!
Technology wasn’t that good Technology wasn’t that good hundreds of years ago!hundreds of years ago!
e- e- e- e- e- e- e- e- e-
The Early 1800’s!
Lots of basic work with electricityLots of basic work with electricity Matter has charge!Matter has charge! There are two types of “charge” in the world:There are two types of “charge” in the world:
+ charged objects+ charged objects - charged objects- charged objects Ben Franklin is the first to come up with these names - Ben Franklin is the first to come up with these names -
+ and -+ and - Franklin didn’t know that these Franklin didn’t know that these
charges were part of the atom - charges were part of the atom - he didn’t even know that atomshe didn’t even know that atomsexisted, yet!existed, yet!
Cathode Ray Tube, or Cathode Ray Tube, or Crooke’s TubeCrooke’s Tube
This was one of the very first This was one of the very first experiments to be done with experiments to be done with electricity! electricity!
A tube containing two metal A tube containing two metal electrodes or plates connected to electrodes or plates connected to a battery - and all of the gas is a battery - and all of the gas is sucked out of the tube!sucked out of the tube!
William Crookes designed this William Crookes designed this tube in 1879tube in 1879
The cathode ray inside glows The cathode ray inside glows greengreen
Crookes was convinced this Crookes was convinced this beam consisted of charged beam consisted of charged particlesparticles
So what are Cathode Rays….?
J.J. Thomson, in 1897, answered this J.J. Thomson, in 1897, answered this question!question!
Thomson used a Crooke’s tube and two Thomson used a Crooke’s tube and two charged plates above and below the beamcharged plates above and below the beam
Which way do you think the beam bent….?Which way do you think the beam bent….? The Beam was attracted to + plate, and was The Beam was attracted to + plate, and was
deflected from – plate!deflected from – plate! From this, he said that the beam was made From this, he said that the beam was made
of negatively charged particles, called of negatively charged particles, called electrons!electrons!
He was looking at electrons, which are part He was looking at electrons, which are part of the atom!of the atom!
These electrons can be easily taken off of These electrons can be easily taken off of atoms, and used as electricity!atoms, and used as electricity!
He also found that a magnet could He also found that a magnet could move the beam as well!move the beam as well!
The cathode ray tube was the beginning to the The cathode ray tube was the beginning to the modern day…..modern day…..
TELEVISION!
Black and White….. Color…….
Millikan Oil-Drop Millikan Oil-Drop ExperimentExperiment
Robert Millikan in 1909 figured out the exact charge and mass Robert Millikan in 1909 figured out the exact charge and mass of an electronof an electron
He placed oil drops in a box, and hit them with electronsHe placed oil drops in a box, and hit them with electrons The oil drops were sprayed into the upper chamberThe oil drops were sprayed into the upper chamber Some drops gained – charge (static electricity)Some drops gained – charge (static electricity)
e -
e -
e - e -
e -
Then Millikan adjusted the Then Millikan adjusted the charge on the plates in the charge on the plates in the bottom of the boxbottom of the box
The - particles attracted to The - particles attracted to the upper plate, because it the upper plate, because it was positivewas positive
It repelled the bottom plate, It repelled the bottom plate, because it was negativebecause it was negative
This suspended the drop in This suspended the drop in space- he made them float in space- he made them float in mid air!mid air!
From this he calculated the From this he calculated the charge and mass of an charge and mass of an electron, knowing the charge electron, knowing the charge on the plateson the plates
The smallest change between The smallest change between two drops was taken to be two drops was taken to be charge of an electroncharge of an electron
e-e-
e-e-
-
+
Now that we have found Now that we have found negative particles….negative particles…. Eugen Goldstein in 1886 used a Crooke’s tube with holes in the Eugen Goldstein in 1886 used a Crooke’s tube with holes in the
negative end and discovered positive particlesnegative end and discovered positive particles He shot a cathode beam (beam of electrons) at hydrogen atomsHe shot a cathode beam (beam of electrons) at hydrogen atoms
e-
e-
e-+
+ ++
+
e-
e-
The electrons from the atoms went with the The electrons from the atoms went with the beam of electrons to the + platebeam of electrons to the + plate
He also saw + particles moving backwards He also saw + particles moving backwards towards the + plate and going through the towards the + plate and going through the holes!holes!
He named these + particles “protons”!He named these + particles “protons”!
++
+
Who puts all of this Who puts all of this information together information together into “The Big Picture”?into “The Big Picture”?
J.J. Thomson theorized that these J.J. Thomson theorized that these negative and positive particles were negative and positive particles were actually part of matter - part of the actually part of matter - part of the atom!atom!
We are all made of charge!We are all made of charge! He develops the first working He develops the first working
model of the atom, known as the model of the atom, known as the PLUM PUDDING MODEL!PLUM PUDDING MODEL!
This rejected Dalton’s idea that This rejected Dalton’s idea that atoms were solid particles like atoms were solid particles like marbles that weren’t made of marbles that weren’t made of smaller piecessmaller pieces
NOT TRUE!
Why was any of this Why was any of this IMPORTANT…?IMPORTANT…?
People didn’t believe in atoms, and didn’t understand People didn’t believe in atoms, and didn’t understand what things like electricity and light were!what things like electricity and light were!
Thomson showed that electricity was nothing more Thomson showed that electricity was nothing more than a flow of little negative particles called electrons!than a flow of little negative particles called electrons!
And electrons, along with protons, make up every And electrons, along with protons, make up every atom, in every person, plant, building and object in the atom, in every person, plant, building and object in the universeuniverse
We are made of charged particles - the same particles We are made of charged particles - the same particles that we use for electricity!that we use for electricity!
Why is Thomson’s model Why is Thomson’s model wrong….?wrong….?
A scientist named Ernest Rutherford figured it out!A scientist named Ernest Rutherford figured it out! He shoots big heavy alpha (He shoots big heavy alpha () particles at ultra thin gold foil) particles at ultra thin gold foil Most of the particles went straight through, and did NOTHING.Most of the particles went straight through, and did NOTHING. A very few were deflected, and some even bounced straight back!A very few were deflected, and some even bounced straight back! Rutherford described this as a bowling ball being sent at a piece of Rutherford described this as a bowling ball being sent at a piece of
paper, full speed, and bouncing back!paper, full speed, and bouncing back!
The Gold Foil Experiment….The Gold Foil Experiment….
What is happening? Why are the alpha particles What is happening? Why are the alpha particles bouncing off?bouncing off?
Gold Foil Experiment…..Gold Foil Experiment…..
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What is going on….?What is going on….? Most of the alpha particles are going straight through!Most of the alpha particles are going straight through! A few of the alpha particles are bouncing off of something!A few of the alpha particles are bouncing off of something! Alpha particles are big, and positive!Alpha particles are big, and positive! What could they be bouncing off of?What could they be bouncing off of? They must be bouncing off of something that is….They must be bouncing off of something that is…. Positive!Positive! And big!And big! Rutherford theorized that all of the protons weren’t scattered Rutherford theorized that all of the protons weren’t scattered
about, like in a chocolate chip cookie, but were all concentrated about, like in a chocolate chip cookie, but were all concentrated into a tiny, dense center, which he called the nucleus!into a tiny, dense center, which he called the nucleus!
The electrons must be orbiting around this nucleus! Why?????The electrons must be orbiting around this nucleus! Why?????
Rutherford’s “nuclear” model!p+p+p+p+p+Nucleusp+p+e-e-e-e-e-e-e-
What is the relative size of the atom….?
An atomic model the size of An atomic model the size of Busch Stadium and parking Busch Stadium and parking would contain a pea sized would contain a pea sized nucleus containing 95.95% of nucleus containing 95.95% of the atoms mass.the atoms mass.
The pea at the pitcher’s The pea at the pitcher’s mound would be the nucleus, mound would be the nucleus, and an ant crawling on the and an ant crawling on the parking lot outside would be parking lot outside would be an electron!an electron!
The atom is mostly…..The atom is mostly….. Empty space! Nothing!Empty space! Nothing!
So is this the final model of the So is this the final model of the atom today…?atom today…?
No!No! A scientist named Neils Bohr, a great A scientist named Neils Bohr, a great
friend of Einstein, noticed something friend of Einstein, noticed something weird about Hydrogenweird about Hydrogen
A hydrogen atom consists of 1 electron A hydrogen atom consists of 1 electron orbiting 1 proton….orbiting 1 proton….
Atoms can give off light when they are Atoms can give off light when they are excited with electricity!excited with electricity!
Think about light bulbs, neon lights, Think about light bulbs, neon lights, headlights….headlights….
With one electron, how many different With one electron, how many different types of energy or colors of light do you types of energy or colors of light do you think hydrogen can give off….?think hydrogen can give off….?
……. Only one color of light!. Only one color of light! Bohr excited hydrogen atoms with high voltage electricityBohr excited hydrogen atoms with high voltage electricity Hydrogen gave off violet light….Hydrogen gave off violet light…. The violet light was actually FOUR DIFFERENT COLORS OF The violet light was actually FOUR DIFFERENT COLORS OF
LIGHT, as viewed through a prismLIGHT, as viewed through a prism How can one electron give off four colors of light???How can one electron give off four colors of light???
HOW IS THIS POSSIBLE…?HOW IS THIS POSSIBLE…?
It doesn’t make sense that one electron can give off four different It doesn’t make sense that one electron can give off four different colors of light!colors of light!
Hydrogen, with only one electron, should be giving off just one color!Hydrogen, with only one electron, should be giving off just one color! Bohr came up with an explanation for this….Bohr came up with an explanation for this…. It involved It involved changingchanging the current accepted model of the atom! the current accepted model of the atom!
It doesn’t make sense that one electron can give off four different It doesn’t make sense that one electron can give off four different colors of light!colors of light!
Hydrogen, with only one electron, should be giving off just one color!Hydrogen, with only one electron, should be giving off just one color! Bohr came up with an explanation for this….Bohr came up with an explanation for this…. It involved It involved changingchanging the current accepted model of the atom! the current accepted model of the atom!
Bohr came up with a new model for the Bohr came up with a new model for the atom…atom… Bohr suggested that it electrons could move to many locations or “energy levels” within Bohr suggested that it electrons could move to many locations or “energy levels” within
the atom!the atom! The electron was moving to more than one location in the atom!The electron was moving to more than one location in the atom! In Bohr’s Model of the atom, electrons orbit the nucleus like planets orbit the sun. It is In Bohr’s Model of the atom, electrons orbit the nucleus like planets orbit the sun. It is
called THE PLANETARY MODEL.called THE PLANETARY MODEL. When electrons jump up to different energy levels, they eventually fall back down and give When electrons jump up to different energy levels, they eventually fall back down and give
off light!off light!
•Electron can jump up, and Electron can jump up, and when they fall back down, when they fall back down, they give off colors of light!they give off colors of light!
The colors we see for The colors we see for Hydrogen……Hydrogen……
The colors we see for The colors we see for Hydrogen……Hydrogen……
Different Different substances give substances give off different off different colors….Why?colors….Why?
CarbonCarbon
HeliumHelium
NeonNeon
Different elements have different electrons, that Different elements have different electrons, that can jump to different places in the atom!can jump to different places in the atom!
Electrons in Energy LevelsElectrons in Energy Levels LevelLevel maximum number of maximum number of
electronselectrons 11 22 22 88 33 88 44 3232
Marble ModelMarble ModelPlum Pudding Plum Pudding ModelModel
The Nuclear The Nuclear ModelModel
The Planetary The Planetary ModelModel
Why is learning about the atom important….?
The atom was considered to be an “imaginary” The atom was considered to be an “imaginary” thing, something that people laughed at! thing, something that people laughed at!
Roosevelt trusted Einstein, and funded his Roosevelt trusted Einstein, and funded his secret research known as the “Manhattan secret research known as the “Manhattan Project”Project”
In a few short years, the idea of an invisible In a few short years, the idea of an invisible atom had been developed into a city-destroying atom had been developed into a city-destroying weapon - the atomic bomb! They figured out weapon - the atomic bomb! They figured out they could split atoms apart, and this would they could split atoms apart, and this would release tons of energy!release tons of energy!
In Hiroshima, of a resident civilian population of 250,000 it was estimated that In Hiroshima, of a resident civilian population of 250,000 it was estimated that 45,000 died on the first day and a further 19,000 during the subsequent four 45,000 died on the first day and a further 19,000 during the subsequent four months. In Nagasaki, out of a population of 174,000, 22,000 died on the first day months. In Nagasaki, out of a population of 174,000, 22,000 died on the first day and another 17,000 within four months. Over 90% of each city was destroyed.and another 17,000 within four months. Over 90% of each city was destroyed.
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Only two atomic bombs have ever been used in wartime history - The U.S. used them both against Japan to end World War II….
Only two atomic bombs have ever been used in wartime history - The U.S. used them both against Japan to end World War II….
The first video shows one of the actual bombs being detonated….The second, the first testing of a “Hydrogen” Bomb…
The first video shows one of the actual bombs being detonated….The second, the first testing of a “Hydrogen” Bomb…