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Alik Manoogian

on 8 October 2015

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Transcript of Atoms

J. J. Thomson's Experiment
Rutherford's Gold Foil Experiment
Bohr's Atomic Model
Friday, October 2, 2015
Vol XCIII, No. 311
Dalton's Atomic Theory
Schrodinger's Wave Mechanical Model
History & Timeline
The experiment was inspired from these factors and outcomes, which are:
His discovery of alpha particle.
His previous study about x-ray.
Rejection of Thomson model from scientists.
The experiment was conducted from 1908 to 1913 under Rutherford's direction.
His initial hypothesis was supported by the experiment's outcome, which was published in 1911 and again in 1913 to give further information discovered.
Who is Ernest Rutherford?
Why did he initiate the experiment?
What is Rutherford's Gold Foil Experiment
Ernest Rutherford was a New Zealander whose parents relocated from England.
In 1895, he gained permission to work and study at the University of Cambridge in England.
In 1907, he decided to move permanently to England.
During WWI, he worked on a top secret project to figure out a way to detect submarines.
During his lifetime, he achieved many awards for his contribution to science, specifically chemistry and physics.
Where did he proceed the experiment?
How was the experiment performed?
The Significance of Rutherford's Gold Foil Experiment
The experiment proved and supported Rutherford's initial hypothesis and rejected Thomson model of an atom.
The experiment proved the existence of a nucleus within an atom and further developed the structure like what it is currently today.
It proved that the nucleus is positively charged and is surrounded with an empty space.
Alpha particles are shot directly onto the thin gold sheet.
A radioactive source is prepared and is placed in a lead box to prevent radiation from spreading out.
A ring of detector is placed around a thin sheet of gold foil to detect alpha particles from the radioactive source.
In 1907, Ernest Rutherford, a new physics professor at the University of Manchester, received a visit from Hans Geiger and Ernest Marsden.
They would later assist him with the experiment.
Rutherford's Gold Foil Experiment was a series of experiments whose purpose is to discover and to prove that every atom contains a positively charged nucleus.
They eventually achieved their original purpose by performed and measured how alpha particle is scattered when comes in contact with a thin gold foil.
Alik Manoogian, Hayden Gallina, and Viet Tran
Written By:
All matter is made of atoms. Atoms are indivisible and indestructible.
All atoms of a given element are identical in mass and properties.
Compounds are formed by a combination of two or more different kinds of atoms.
A chemical reaction is a rearrangement of atoms.
John Dalton was of Quaker bakground and an English chemist
Known primarily for his atomic theory, although he made many other discoveries in the field of chemistry
study of colorblindness (Daltonism)
a pioneer meteorologist
fascination with the weather and atmosphere= further research into the nature of gasses
History & Timeline
The Significance of J.J. Thomson's Experiment
The experiment was proceeded at the Victoria University of Manchester (today University of Manchester).
Atomism (the atom and void)
4th century BCE in India- Kanada
five elements were air, water, earth, fire, and space
5th century BCE in Greece- Leucippus and Democritus
all matter composed of small indivisible particles called atoms
Aristotelian philosophy
acceptance of the four elements of air, water, earth, and fire, but not atomic theory
up until the 16th century CE Aristotelian philosophy was most widely accepted
18th century in Europe- Isaac Newton and John Locke
ideology that puts reality and change in terms of corpuscles
unlike atomism, corpuscles could be divided
Law of Conservation of Mass (1789)
Antoine Lavoisier
Law of Definite Proportions (1799)
Joseph Louis Proust
In 1897, J.J. Thomson discovered electrons by experimenting and measuring cathode rays.
England's Lake District (Cumberland) and Manchester
In 1904, because of his discovery of electrons, he suggested the Thomson Model.
In 1894, he began studying about cathode rays.
A theory proposed in 1808 stating...
Interest in meteorology>>
Further research into gasses
Evaporated water exists as its own gas
Air occupies the same space as the water
Solids cannot occupy the same space as each other, and the gasses must therefore be composed of small particles
He wanted to explain how and why these elements could compine in ratios
Initial observations of gasses
Water absorbed carbon dioxide better than it did nitrogen
Water and air particles were able to coexist and mix together
These paired with the Law of Conservation of Mass and the Law of Definite Proportions allowed him to develop the Law of Multiple Proportions
Additionally, he hypothesized that different elements combined at different fixed rations due to their different atomic weights and complexities
His atomic theory explained why the Law of Multiple Proportions was valid
The establishment of a first scientific theory of an atom
Basis to nearly all other advances in the study of atoms
Dalton's Atom Model
"Billiard Model"
Dalton believed atoms to be single units that could not be broken down, and therefore saw them as solid spheres
Bohr realized that electrons moving around impacted physical and chemical characteristics of atoms. (3)
Bohr's atomic model has had a
huge impact on the world. His model gave us a better understanding of what atoms look like, and how they are built up. Although parts of his model are incorrect, he still has had a large impact on the world. (1) (2)
A British physicist who discovered the electron with experiments created to study the electric discharge in a cathode tube. (3)
A well-known Cavendish lab in Cambridge, England
Experiment 2
Objective: Prove that cathode rays carried a negative charge
Bohr worked with J.J. Thompson and was introduced to Rutherford. Rutherford's model showed electrons moving in random motion, and Bohr had evidence that the electrons moved in stable orbits around the nucleus. (2) (1)
Neils Bohr was a Danish physicist who contributed heavily to peoples understanding of the atomic theory and structure.. (2)

Bohr conducted his experiments to prove that electrons move in a stable motion around the nucleus. He wanted to help people understand what atoms look like. (1)

Bohr made his discoveries while working with and under J.J. Thompson in England. (2)

Bohr's model is a model that shows how electrons move in a stable motion around the nucleus. (1)
(1): Rutherford's Experiment - Part I: 1906 to Early 1911

(2): Rutherford's Experiment - Part II: The Paper of 1911

(3): Ernest Rutherford Biography

Experiment 3
Objective: Measure charge and mass of particles
Series of experiments (3): designed to study the nature of electric discharge in a cathode-ray tube
Experiment 1
Objective: Prove that the rays emitted by the cathode were inseparable
Experiment 1:
Cathode ray tube with metal cylinder, two slits that led to electrometer, and electrometers that measured the electrical charges.

Experiment 2:
After improvement of the quality of the cathode ray tube and vacuum, positive and negative plates placed on the tube

Experiment 3:
Determine the charge and mass by how much different electrical currents of varying strengths bent them
Experiment 1
Electrometers measured no charge when there was a magnetic field; cathode rays were charged and were deflected by magnets; thus charges and rays were intertwined and together.
Experiment 2
Rays deflected by electric plates; positive plate attracted them, and negative plate deflected them; thus, charges bound to the rays and consisted of "corpuscles" or electrons that were negatively charged.
Experiment 3
Charge-to-Mass ratio was very large, so either the charge of particles was very large or mass was very small.
Thomson Model
"Plum Pudding Model"
1): Elements and Atoms: Chapter 16

1) Atomism before Dalton by Leopold May http://pubs.acs.org/doi/abs/10.1021/bk-2010-1044.ch003

2) John Dalton's Atomic Model by Matt Williams http://www.universetoday.com/38169/john-daltons-atomic-model/

3) John Dalton by Sydney Ross http://www.britannica.com/biography/John-Dalton

4) Dalton's Atomic Theory http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html
(4): http://chemteacher.chemeddl.org/services/chemteacher/index.php?option=com_content&view=article&id=74

(5): http://myweb.usf.edu/~mhight/goldfoil.html

(6): Alpha Particles and the Atom

(7): Rutherford's Gold Foil Experiment
2) JJ Thomson's Experiments with Cathode Ray Tubes http://ericsaltchemistry.blogspot.com/2010/10/jj-thomsons-experiments-with-cathode.html
1) ERWIN SCHR÷DINGER (1887 - 1961) http://www.physicsoftheuniverse.com/scientists_schrodinger.html

2) The Cloud Model http://www.regentsprep.org/Regents/physics/phys05/catomodel/cloud.htm

3) Atomic Theory http://www.msnucleus.org/membership/html/jh/physical/atomictheory/lesson1/atomic1g.html

4) Historical Models of the Atom http://www.commonsensescience.org/atom_models.html

5) Modern Atomic Theory: Models http://www.abcte.org/files/previews/chemistry/s1_p6.html

6) The Physics Behind Schrödinger's Cat Paradox by Melody Kramer http://news.nationalgeographic.com/news/2013/08/130812-physics-schrodinger-erwin-google-doodle-cat-paradox-science/

7) Schrodinger Equation http://hyperphysics.phy-astr.gsu.edu/hbase/quantum/schr.html

Erwin Schrödinger was an Austrian physicist who is one of the founders of quantum mechanics.
Developed the "electron cloud model"
Developed the Schrödinger Equation
Austria (mainly Vienna) and England (Oxford University)
The quantum mechanical model of an atom that does not provide an exact path of the electrons, but predicts the odds of the location of the electron.
Schrodinger Equation
Predicts the behavior of a complex system
As a wavefunction, it predicts the outcomes and possibilities precisely
the outcome can be a large number of events and the equation predicts the distribution of results
Had the help of Werner Heisenburg, and they used the mathematical equation of the behavior of waves developed by Louis de Broglie, a French theorist.
As a theoretical physicist who studied under many people, Schrodinger was interested in Bohr's model. He developed the idea in a slightly different direction creating a mathematical model that incorporated de Broglie's ideas and it was based on quantum mechanics.
Schrodinger's Cat is a paradox that was developed in order to illustrate the nature of wave particles in quantum mechanics.
Just as Schrodinger's Cat explains all the possible existences of the cat, at the heart of quantum theory with wave function is the explanation of all the possible states that particles can have, such as the electrons.
Thus, the idea is that without observation, we cannot know exactly what something is doing, only the probabilities, no matter how small each probability is.
1) Bohr Atomic Model http://abyss.uoregon.edu/~js/glossary/bohr_atom.html
3) Joseph John Thompson http://www.chemheritage.org/discover/online-resources/chemistry-in-history/themes/atomic-and-nuclear-structure/thomson.aspx
In cathode tubes, switching on voltage could make fluorescent lines of electricity travel from the bottom to the top of the tube. The problem was that nobody had any idea how it worked. J.J. Thompson wanted to find out how it worked. (4)
4) Discovery of the Electron http://www.pbs.org/transistor/science/events/electron.html
2) Neils Bohr-Important Scientists http://www.physicsoftheuniverse.com/scientists_bohr.html
Does not show function of atoms, but their structure

Basis of the Quantum Mechanical Model of the atom

Represents the beginning of the modern atomic theory
5) J.J. Thomson Biographyhttp://www.biography.com/people/jj-thomson-40039
It acts as one of the stepping stones of modern atomic theory.
(3) Neils Bohr: Odyssey of the Atom https://www.msu.edu/~ramseys3/lbs171h/index.htm
Full transcript