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Period 5.
Scientist’s Early Theories on the Atom
By Corey Lacher
and Grant Miller
Democritus
• He was born into considerable wealth which allowed him to travel and research more than a common citizen
• He studied in Egypt at the ancient schools, which specialized in philosophy and mathematics.
• After he finished his studies, he was impoverished and considered insane among his people.
• Leucippus was Democritus’ mentor.
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Leucippus
• His date of birth or his parents’ status is unknown, however it is estimated that he was born into the upper middle class
• A lot of Leucippus’ theories are to contradict his teacher, Zeno
• After growing up, he moved to Abdera where he began his own studies with his student Democritus.
http://plato.stanford.edu/entries/leucippus/#2
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reich-chemistry.wikispaces.com
Democritus Atomic and Leucippus Theory
• Because of the close relationship between Leucippus and Democritus, their atomic theories are very alike.
• The first theory, created by Leucippus said there is an infinite amount of two elements, the solids and the void.
• This theory was changed during Democritus’s studies, and finally published.
http://plato.stanford.edu/entries/leucippus/#2
Atomic Theory
• Proposed atomic theory of matter
• Proposed that contrary to belief matter could not be divided forever
• Proposed the idea of an atom-the smallest matter can be divided and still be the same substance
http://www.funsci.com/fun3_en/democritus/democritus.htm
Aristotle
• Greek philosopher• Student of Plato, teacher of Alexander the
Great• Educated as aristocracy• Physics, Metaphysics, Nicomachean Ethics,
Politics, De Anima (On the Soul) and Poetics, important works
• Studied many sciences• Scientific method
http://en.wikipedia.org/wiki/Aristotle
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Atomic Theory
• Proposed matter can divided infinitely
• Due to being highly regarded as scholar, stuck for 2000 years
http://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htm
Antoine Lavoisierand The Law of Conservation of
Matter
By John Chiavelli and Joey Miller
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Biography
• Born to a wealthy Paris family and completed a degree in law
• He dreamed of studying mathematics and science, and soon gained membership into France’s most prestigious Science Academy
• He married Marie-Anne Pierrette Paulze, who became his scientific colleague
• She translated notes, drew sketches, and developed a scientific mind
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Continued…
• Known for the Law of Conservation of Matter/Mass
• Implemented the Metric System in France
• Would go on to be the architect of the chemistry revolution
• Known as the Father of Modern Chemistry
• Guillotined at age 51, found guilty of conspiracy against the people of France
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The Phlogiston Theory
• Chemistry was very underdeveloped at the time
• A weightless or nearly weightless substance known as phlogiston. Metals and fire were considered to be rich in phlogiston and earth was considered oxygen poor
• Stated that weight loss during combustion was a result of a loss of phlogiston
• When metal is calcined, or roasted in the presence of air, it turns to a powdery substance called a calx
• However, when some metals were calcined, the resulting calx was heavier than the initial metal
• Scientists tried to come up with explanations, but the theory was WRONG***
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The Law of Conservation of Matter/Mass
• Was an anti-phlogistonist
• Designed an experiment to disprove the theory
• He heated mercury in a jar for 12 days, red mercury calx formed, and the volume of air in the jar decreased
• The remaining air was nitrogen, and heating the calx produced the air that had decreased
• The sequence of experimentation established that heat caused the formation of calx, and stronger heating reverted it back to the original substances
• Hg(l) + O2(g) -> HgO(s) and then HgO(s) -> Hg(l) + O2(g)
• THEORY DISPPROVED
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• ***The law of conservation of matter states that matter is neither lost nor gained in traditional chemical reactions; it simply changes form.***
• The state in which a substance is may change in a chemical reaction, for example, from a solid to liquid to a gas but its total mass does not change.
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Significance of Concept
• Changed chemistry from qualitative to quantitative science
• Put an end to the Phlogiston Theory, by proving that the mass of the reactants is equal to that of the products
• He later showed that oxygen was responsible for weight differences associated with combustion
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Continued…
• Acceptance of the Phlogiston Theory dissipated
• The Law of Conservation of Matter became accepted
• A major turning point in the world of chemistry
• Chemistry further developed into a vast scientific field
• Antoine Lavoisier is known as the Father of Modern Chemistry
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Joseph Proust. Born on Sept. 26, 1754 in Angers, France
. His father was apothecary of Angers
. Studied chemistry in father’s shop
. Became apothecary at prestigious Salpetriere hospital
. Taught chemistry with famous chemist and physicist Pilâtre de Rozier
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http://en.wikivisual.com/index.php/Joseph_Proust
http://www.answers.com/topic/joseph-proust
Joseph Proust’s Later Life. Went to Spain to teach at Chemistry School of Segovia and University of Salamanca
. Napoleon invaded Spain and his army burnt Proust’s laboratory
. Forced to go back to France as a result
. Died on July 5, 1826 in Angers
. During his lifetime, studied the sugars in fruits and vegetables (glucose) and created the Law of Definitive Proportions
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http://iml.jou.ufl.edu/projects/fall03/pfeiffer/university.htm
http://en.wikipedia.org/wiki/Joseph_Proust
Law of Definite Proportions-A chemical compound contains
the same proportions of elements by mass
-All of one type of compounds have the same make up
-Ex:The mass of Pure water is always 8/9ths oxygen and 1/9
hydrogen
-Makes up part of modern chemistry
Law of Definite Proportions(Exceptions)
-The law is not always true -Non-stoichiometric compounds composition
can vary from sample to sample-Chemical Compounds with compositions that
can not be defined by ratios of real numbers-Ex:Iron Oxide Wustile- Levels and mass of
oxygen and iron can differ
http://en.wikipedia.org/wiki/Law_of_definite_proportions
Effect Upon Chemistry Society• Initially upon first publish there was much
controversy among fellow chemists especially Berthollet, who believed the opposite of what Proust was trying to say; elements could come in any proportion.
• The laws of definite proportion created the basis for the development of the atomic theory by John Dalton mere years later.
• Dalton also came up with the law of multiple proportions, which in combination with the law of definite proportions, helped to begin stoichiometry (the science of chemical reactions).
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Effect Upon Chemistry Society (cont’d)• His law helped lead to chemists being able to create compounds and learn
their properties more because knowing the ratio of elements is all they need. Naturally its also useful in identifying compounds.
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- For example, we know that Steel is always almost completely made of Iron with a bit of Carbon and other small elements.
•Although it is a chemistry principle it does have its practical uses.
•This law makes it easy to modify a baking recipe according to the amount you want to produce.
http://en.wikipedia.org/wiki/Law_of_definite_proportions
http://www.britannica.com/EBchecked/topic/480555/Joseph-Louis-Proust/260847/Law-of-definite-proportions
http://www.ehow.com/about_4570091_law-definite-proportions.html
John Dalton
• Born: September 6th, 1766 in Eaglesfield, England
• Died: July 27th, 1844 of a stroke
• English chemist and physicist
http://www.universetoday.com/38193/john-daltons-atomic-theory/http://dl.clackamas.edu/ch104-04/dalton%27s.htmhttp://www.nndb.com/people/278/000049131/
Background Information
• Had two siblings: Jonathon and Mary • Was a farmer for two years • Discovered color blindness• Learned math from a distant relative, Elihu
Robinson• Went to work at a school in Kendal for his
cousin George• Became a teacher at York College• Is most widely known for his atomic theory
Dalton’s Atomic Theory• Elements are made of small particles called
atoms.• All atoms for a particular element are identical
and have the same mass.• Atoms of different elements can combine in a
chemical reaction to form chemical compounds in fixed ratios.
• [In a chemical reaction] atoms cannot be created or destroyed; only rearranged.
The Atomic Theory: Explanation/Significance
• It explains a lot of chemical properties; for example, how atoms can combine to form molecules
• It explains chemical change better than previous theories (the Particle Theory) had
• It confirms the basic laws of chemistry: Definite Proportions and Conservation of Mass
The Law of Multiple Proportions --Also known as “Dalton’s Law”
-- It is part of what laid the foundation for Dalton’s atomic theory, and the basis of
chemical formulas for compounds
-States that when elements combine in more than one proportion, they do so in the ratio
of small who numbers (under the assumption that they have the same type of
chemical bond)--Example: carbon and oxygen react to form CO
or CO2, but not CO1.4
Law of Multiple Proportions (continued)
Example:
2 carbon oxides: CO and CO2
The ratio for the first is 1/1
The ratio for the second is 1/2
The ratio between these ratios is a ratio between small whole
numbers, or
1/1 : 1/2= 2:1
- This proves that the law is consistent with the use of
chemical formulas
JJ THOMSON
CATHODE RAY TUBE
Full Name: Joseph John ThomsonDecember 18, 1856 – August 30 1940
Born in Cheetham Hill in Manchester, EnglandPrivate School Education
Attended Owens College at age 14
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•Transferred to Trinity College after his father died•Became Cavendish Professor of Physics, with Ernest Rutherford as a student•Married Rose Elizabeth Paget, daughter of a physician, and fathered one son and one daughter•Seven of his research assistants got Nobel Prizes and his son won in 1937 for proving the wavelike properties of electrons•He was awarded the Nobel Prize in 1906 in recognition of the great merits of his theoretical and experimental investigations on the conduction of electricity by gases•In 1918 he became master of Trinity College, Cambridge and remained there until his death in 1940
JJ THOMSON
CATHODE RAY TUBE•Thompson investigated the nature of matter which led him to create an experiment testing a charged particle •In the Cathode Ray Tube, an electric current generates a beam that strikes through a hole on the other end of the tube•A fluorescent coating is added to the ray to make it visible to human eyes•There is a magnetic field around the ray, proving that it has mass•The rays path is also affected by an external electric field, determining that the ray is charged
CATHODE RAY TUBE•By studying the deflections of the tube due to the fields, Thompson determined the mass to charge ratio of the beam particles•He found the mass-to-charge ratio to be thousands of times smaller than hydrogen, the lightest element, meaning they were extremely light or very highly charged•He discovered that the beam was negatively charged
SIGNIFICANCE•his research proved the existence of negatively charged particles, later called electrons•proved atoms can be divided•Created the plum pudding model of the atom which was later proved wrong by Ernest Rutherford•Lead to later experiments with the electron
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SIGNIFICANCE•Contribution in the development of cathode ray tubes•Lead to research in subatomic particles•When a solid object was put in the path of cathode rays a shadow appeared showing that cathode rays traveled in straight lines.•The cathode rays were deflected by electric and magnetic fields meaning they were composed of charged particles.•When a paper wheel was placed in the path of the cathode rays, the cathode rays struck it and made it rotate, proving that cathode rays were made of particles
Robert Milikan Background: -March 22, 1868 - December 19, 1953
-Went to high school in Iowa (lived in a rural era)
-Went to Oberlin College and then Columbia University
-Wife = Greta Erwin Blanchar
-Three sons: Clark Blanchard, Glenn Allen, and Max Franklin
-Received his Ph.D. in 1895
-Made numerous discoveries in the fields of electricity, optics, and molecular physics (contributions to science were with the research of cosmic rays).
-Was an author (wrote in scientific journals) that were really well-respected in science community
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Robert Milikan Background: •Held highly esteemed scientific
positions:•President of the American Physical Society •Vice-President of the American Association for the Advancement of Science
•Held honorary doctor’s degrees from 25 universities
•Set a goal to write textbooks that would capture the attention of readers that was easy to understand
•Vice-Chairman of the National Research Council during WWI playing a major part in developing anti-submarine and meteorological devices
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http://www25.uua.org/uuhs/duub/articles/robertmillikan.html
The Experiment: Oil-Drop-Major success was
determining charge of an electron, using the elegant "falling-drop method" called Milikan Oil Drop
-Proved that electric charge is quantized (as predicted by quantum physics)
-Discovery was accomplished by spraying minute drops of oil into a specially built chamber
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http://millikan.nbaoh.com/1.htm
The Experiment: Oil-Drop-How the experiment operated:
1. Atomizer produces oil droplets2. Oil Droplets fall through the hole3. X-rays negatively charge the droplets4. Voltage applied to 2 plates creates an electric field and the electric force pulls some oil drops up5. Microscope measures the rate at which the oil drops fall or rise
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http://commons.wikimedia.org/wiki/File:Simplified_scheme_of_Millikan%E2%80%99s_oil-drop_experiment.png
The Experiment: Oil-Drop-Drops travel up/down
depending on the forces acting on it
-1st: experiment is done without an electric field = gravity pulls the drops down because its force is greater than air resistance-Then done W/ electric field = electric force larger than gravitational pull causing droplets to go up
-Using this formula: you can find velocity (velocity is related to charge), thus finding the charge of an electron
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W/O Electric Field
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Significance of the Experiment
-First successful scientific attempt to detect and measure the effect of an individual subatomic particle
-The Millikan oil drop experiment was so significant that Millikan won the 1923 Nobel Prize in physics for his work
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Significance of the Experiment
-Expanded upon Cathode-Ray experiment which determined mass/charge ratio but didn’t determine the numbers for it
- He determined the numbers for the ratio-Determined charge of electron through oil-drop experiment
-Determined that an electron is a sub-atomic particle
-Determined that charge is quantized
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• 1871- 1937
• “Father of nuclear physics”
• Early on in his life, he developed a device to detect electromagnetic waves
•Left home in New Zealand to study at Caterbury University as a researchstudent on a scholarship
•His professor, J.J. Thompson recognizedhis potential and invited Rutherford to work with him
• After radioactive atoms were discovered, he became highly interested in radioactivity
• He discovered that radioactive atoms gave off two different types of rays: alpha and beta rays (alpha= made up of positively charged particles; beta= made up of negatively charged particles
• Returned to New Zealand for marriage butcontinued his research at McGill University
• He researched into radioactivity,discovering radon
• Published the book, Radioactivity, and won theNoble Prize in chemistry for his work on the transmutation of elements and the chemistryof radioactive substances
• Is most famous for his Gold Foil Experiment
• Rutherford came up with the earliest version of the atomic model when he conducted his gold foil experiment
•When firing alpha particles at a fine sheet of gold foil, he found that some particles pass through the foil, whilesome change direction orpass back
• He concluded that the atoms of gold foil must bemostly empty space around a dense nucleus and cameup with his atomic model
1.Downfall of the Plum Pudding Model
2.Creation of the Atomic Model
• J.J Thompson’s Plum Pudding Model claimed that the negatively charged electrons were embedded in a sphere of positive charge so the charges were balanced
• WAS INCORRECT since none of Thompson’s electrons contained enough charge or mass to deflect alphas strongly
• ** INSTEAD, Rutherford suggested in his Atomic Model that a large amount of the atoms charge and mass is instead concentrated into a very small region giving it a high electric field
• Rutherford propsed that the atom was mostly empty space
Sir James Chadwick
1891 - 1974
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Early Life
• Born October 20, 1891• Born in Cheshire, England• Graduated from Honours School of Physics in 1911• Studied under Ernest Rutherford in the Physical
Laboratory in Manchester for 2 years• Gained his Master of Science degree in 1913
Scientific Context
• Ernest Rutherford recently discovers the proton
• Henri Becquerel recently discovers gamma waves
• Beginning to develop accurate atomic model
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Experiment
• Sample of Beryllium bombarded with alpha particles (type of radiation)
• Caused Beryllium to emit different radiation
• Knew radiation was neutral because it was not affected by a magnetic field
• Knew the particles were large because they discharged protons
Experiment
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Discoveries
• Leads to discovery of the neutron (1932)
• Discovers mass of the neutron
Significance
• Previously, mass number was always much higher than atomic number
• Neutrons solved this problem
• Atomic model more accurate
• Receives Nobel Prize in Physics in 1935
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Significance
• Made the development of the atomic bomb possible
• Now understood how isotopes worked
• Used uranium 235 to create bomb
• Chadwick worked on Manhattan Project
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Niels Bohr and the Bohr Model
By Tim Hwang and Noah Pardes
Born: October 7, 1885Died: November 18, 1962
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http://www.lucidcafe.com/library/95oct/nbohr.html
About Niels Bohr• Born in Copenhagen, Denmarck on October 7,
1885• His father is Christian Bohr who was a professor
of physiology at the University of Copenhagen.• His mother is Ellen Adler Bohr.• His brother is Harald Bohr who was a
mathematician • Enrolled as an undergrad at the University of
Copenhagen in 1903 and graduated with a doctrine in 1911.
• Marries Margrethe Nørlund in 1912.
About Niels Bohr Cont.• In 1913, he published his theory on the
structure of the atom which was based on Rutherford’s theory.
• Niels Bohr becomes the professor of physics at the University of Copenhagen in 1916.
• He died in Copenhagen on November 18, 1962
Main Point
• Electrons orbit the nucleus in orbits that have a set size and energy.
• The energy of the orbit is related to its size. The lowest energy is found in the smallest orbit.
• Radiation is absorbed or emitted when an electron moves from one orbit to another.
• The simplest example of the Bohr Model is for the hydrogen atom (Z = 1) or for a hydrogen-like ion (Z > 1), in which a negatively-charged electron orbits a small positively-charged nucleus-char
Main Point Cont.• When an electron is in an "allowed" orbit it does not radiate.
Thus the model simply throws out classical electromagnetic theory
• When an electron absorbs energy from incident electromagnetic radiation, it "quantum jumps" into a higher energy allowed state. This higher energy state corresponds to an allowed orbit with a higher value of the integer n
• When an electron is in a higher energy state, it can quantum jump into a lower energy state, one with a smaller value of n, emitting all of its energy as a single photon of electromagnetic energy
Significance• The significance of the Bohr model is that it states
that the laws of classical mechanics do not apply to the motion of the electron about the nucleus
• Bohr proposed rather that a new kind of mechanics, or quantum mechanics, describes the motion of the electrons around the nucleus
• The Rutherford-Bohr model provided the first really useful view of the atom
• It matched what scientists knew about chemical reactions and the way atoms behaved
Significance Cont.
• It matched what scientist knew about chemical reactions and the way atoms behaved
• The Bohr model of the atom deals specifically with the behavior of electrons in the atom
• While he realized electrodynamics is useless, he proposed to use "mechanics" to describe the motion of an electron in its orbit
Work Cited
• http://www.lucidcafe.com/library/95oct/nbohr.html• http://en.wikipedia.org/wiki/Niels_Bohr• http://nobelprize.org/nobel_prizes/physics/laureates/
1922/bohr-bio.html• http://chemistry.about.com/od/atomicstructure/a/bohr-
model.htm• http://www.upscale.utoronto.ca/PVB/Harrison/
BohrModel/BohrModel.html• http://www.lycos.com/info/bohr-model--electrons.html• http://www.chemteam.info/Electrons/Bohr-Model-
part1.html
Citations
• http://www.visionlearning.com/library/module_viewer.php?mid=56
• http://mattson.creighton.edu/History_Gas_Chemistry/Lavoisier.html
• http://cti.itc.virginia.edu/~meg3c/classes/tcc313/200Rprojs/lavoisier2/home.html#phlogiston
Citations-http://martine.people.cofc.edu/111LectWeek1.htm?referrer=webcluster&-http://en.citizendium.org/wiki/Image:Carbon_with_oxygen.JPG-http://www.iscid.org/encyclopedia/Law_of_Multiple_Proportions-http://dictionary.reference.com/browse/law+of+multiple+proportions-http://www.brightstorm.com/science/chemistry/matter/law-of-definite-proportions-law-of-multiple-proportionss
http://www.solarpowerwindenergy.org/wp-content/uploads/2009/05/kineticandpotentialenergy.jpg
http://library.thinkquest.org/3659/energy/matterandenergy.html
http://www.visionlearning.com/library/module_viewer.php?mid=56
http://cti.itc.virginia.edu/~meg3c/classes/tcc313/200Rprojs/lavoisier2/home.html#phlogiston
http://mattson.creighton.edu/History_Gas_Chemistry/Lavoisier.html
http://sciencepark.etacude.com/chemistry/law.php
http://www.ehow.com/about_4568411_law-conservation-mass.html
http://www.britannica.com/EBchecked/topic/684121/chemical-bonding/43364/The-law-of-conservation-of-mass
http://www.homeoint.org/morrell/articles/pm_origin.htm
http://www.ssplprints.com/image.php?id=100610
http://en.wikipedia.org/wiki/Wikipedia:Featured_picture_candidates/Antoine_Lavoisier http://commons.wikimedia.org/wiki/File:Lavoisier_decomposition_air.png
http://cstl-csm.semo.edu/mcgowan/ch181/atomhist.htm
http://www.famousdead.com/antoine-lavoisier/
http://www.scienceshorts.com/lavois.htm
http://www.iss.k12.nc.us/schools/mountmourne/lalerch/shmetric.htm
http://letsgotribe.mlblogs.com/archives/2007/10/the_tribe_pulls.html
http://www.rjdposters.com/Store/DrawProducts.aspx?Action=GetDetails&ProductID=621&ParentID=&PageID=75
http://www.philiplarson.com/e1.shtml
http://reich-chemistry.wikispaces.com/timothy.hitchings.atomichistory.fall.2009
http://www.daviddarling.info/encyclopedia/C/combustion.html
http://www.silkywater.com/waterintro.htm
https://www.msu.edu/~moorean4/TestSite/chemistrymain.htm
http://www.mpch-mainz.mpg.de/~sander/chem-intro.html
http://www.proprofs.com/quiz-school/story.php?title=periodic-table-quiz
http://en.wikipedia.org/wiki/J._J._Thomson
http://www.experiment-resources.com/cathode-ray.html
http://members.chello.nl/~h.dijkstra19/page3.html
http://www.tutorvista.com/physics/jj-thomson-cathode-ray-tube
freepatentsonline.com
http://www.kentchemistry.com/links/AtomicStructure/JJThompson.htm
http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_02&folder=cathode_ray
SOURCES Thomson
http://nobelprize.org/nobel_prizes/physics/laureates/1923/millikan-bio.html http://www.wwnorton.com/college/chemistry/gilbert2/tutorials/interface.asp?chapter=chapter_02&folder=millikan http://www.light-science.com/millikan.html
Citations Millikan
http://www.goalfinder.com/product.asp?productid=69
http://www.juliantrubin.com/bigten/millikanoildrop.html
http://chemistry.about.com/od/electronicstructure/a/millikan-oil-drop- experiment.htm
http://ffden-2.phys.uaf.edu/212_fall2003.web.dir/ryan_mcallister/slide3.htm
• http://christchurchcitylibraries.com/kids/famousnewzealanders/ernest.asp
• http://en.wikipedia.org/wiki/Ernest_Rutherford
• http://mysciencearticles.com/page/8/•http://www.britannica.com/EBchecked/topic-art/41549/18103/Shell-atomic-model-In-the-shell-atomic-model-electrons-occupy•http://picasaweb.google.com/lh/photo/HTbtGA9m7iMKVP8ry_drhw •http://reich-chemistry.wikispaces.com/Fall.2008.MMA.Haley.Timeline •http://www.natlib.govt.nz/collections/online-exhibitions/20th-century-scientists/ernest-rutherford
Sources Chadwick• http://www.suite101.com/content/the-discovery-of-the
-neutron-a46060• http://nobelprize.org/nobel_prizes/physics/laureates/1
935/chadwick-bio.html• Portrait:
http://nobelprize.org/nobel_prizes/physics/laureates/1935/chadwick-bio.html
• Nobel Prize Image: http://startswithabang.com/?p=982
• Rutherford Image: http://www.mlahanas.de/Physics/Bios/ErnestRutherford.html
Sourceshttp://en.wikipedia.org/wiki/Neutronz
http://hyperphysics.phy-
astr.gsu.edu/hbase/particles/neutrondis.html
http://www.suite101.com/content/the-discovery-of-the-neutron-a46060
Becquerel Image: http://nobelprize.org/nobel_prizes/physics/laureates/1903/becquerel-bio.html
Mushroom Cloud Image: http://www.allamericanpatriots.com/photos/mushroom-cloud