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Development of the Atomic Theory

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Vickie Reljin

on 30 January 2013

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Transcript of Development of the Atomic Theory

The Atomic Theory The Development of the Atomic Theory 400 - 300 B.C. He came up with the idea that everything is made up of atoms and they can't be broken into smaller parts. He was only partly correct. What did Dalton believe? John Dalton He thought that the negatively charged particles were spread out in a positively charged atom. He discovered, using a cathode ray, that there seemed to be negatively charged particles in atoms, making them able to be split even further. No one else before him believed that atoms could be split further, besides Aristotle who believed they could be divided infinitely. We call the particles he discovered, electrons. Ernest Rutherford He came up with the idea that electrons traveled in shells, or certain energy levels around the nucleus. No one else before him thought this. Rutherford had thought that electrons circled in orbits, but that was not the same. There can only be a certain amount of electrons on a certain shell. See the diagram below. Niels Bohr Democritus Aristotle Aristotle believed matter was NOT made up of atoms but was made up of the elements: earth, air, fire, and water. He also believed it could be divided forever. 2000 years later... Dalton believed...
That matter was made up of atoms. This agreed with Democritus's idea but challenged Aristotle's.
Atoms can't be broken down further. This also agreed with Democritus but disagreed with Aristotle.
Atoms of the same element are exactly the same.
Compounds can be formed by combining two or more atoms of different elements.
Chemical reactions simply rearrange the atoms. 1808 A.D. J.J. Thomson 1897 A.D. What did he do? Gold Foil Experiment In the gold foil experiment, some of the alpha particles are deflected off something and don't pass through like most others.This experiment showed that, while most of the atom was made up of empty space, there is a small dense center, which we call the nucleus. The nucleus is positively charged. This is different than ideas of others before him because no one else, besides Thomson and his electrons, believed that atoms could be broken into smaller particles. These things were incorrect but they weren't questioned for a very long time... Rutherford's Atomic Model Nucleus Orbits He said that the atom's chemical properties are determined by the number of electrons in the outer levels of an atom. Because there can only be a certain amount in each orbit, the more electrons it has, the more levels it has to have. If electrons gain energy, they move to higher energy levels and move to lower energy levels if they lose that energy. Fun Fact!
He named these particles atoms after the Greek word atomos, meaning "unable to be cut or divided". Fun Fact!
Both him and his brother were color blind! Fun Fact!
He became a teacher at the school where he went when he was only 12 years old! Fun Fact!
His real name was Joseph John but everyone called him J.J. Fun Fact!
He won the Nobel Prize in physics in 1906! Fun Fact!
In 1908, he was knighted by the King! Fun Fact!
He won a Nobel Prize in chemistry in 1908! Fun Fact!
He had an element named after him!
It is called rutherfordium. Works Cited
Information about Democritus:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 113.
Fun Fact about Democritus:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 113
Picture of Democritus: http://bit.ly/S6kTWH
Picture of Democritus's atomic model: http://bit.ly/RXYOrs Inside an Atom! Protons! +
+ +
+ + Positive charge! Found in the nucleus! Neutrons! O O

O O No charge! Found in the nucleus! + +
+ Electrons! -
- -
- - - -
- - Section 2 Found orbiting the nucleus! Negative charge! Mass: about 1 amu Mass: about 1 amu Mass: about 0.0005486 amu (over 1800 times smaller than a proton or neutron!) Fun Fact!
In 1922, Bohr won the Nobel Prize in physics. Fun Fact!
He also had an element named after him! It is called bohrium. Who discovered neutrons? His name is James Chadwick! This guy! Fun Fact!
He also won the Nobel Prize for physics! He won in 1935. Fun Fact!
His birthday is the same as mine (October 20), only he is 106 years older! Fun Fact!
He had twin daughters! Actually, he only proved the existence of neutrons. Others, like Ernest Rutherford, already predicted their existence. Chadwick, however, was the one who conducted the experiment that proved there were, in fact, neutrons. Fun Fact!
He was knighted in 1945. After discovering the nucleus, he found something inside of it! In 1919, he discovered that there seemed to be a positively charged particle in the atom's nucleus. He called this the proton. 1909 A.D. These are the steps in the experiment he used to discover neutrons:
1. Sent alpha particles at a Beryllium sample.
2. The Beryllium released a neutral radiation.
3. The radiation goes through paraffin, a proton-rich surface.
4. The radiation pulled some of the protons from the paraffin along with it, making it charged.
5. The positively charge radiation went into a gas chamber where it ionized the gas, or made the atoms charged.
6. These atoms went toward an electrode, or a place where electricity come or leaves something.
7. This caused a current which Chadwick measured to find that there were, in fact, particles that were only slightly larger than protons and had no charge. Information about James Chadwick:
Fun Facts about James Chadwick:
Picture of James Chadwick: http://bit.ly/QvcWcc
Picture of Chadwick's atomic model: http://bit.ly/WwEHG3 Isotope information:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 122.
Average Atomic Mass: http://bit.ly/XzmAgC
Picture of Lead: http://bit.ly/TmFjNO
Atomic Mass of Lead:
Inside the Atom! Information: http://www.citycollegiate.com/atomic_structureXIg.htm Information about Niels Bohr:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 128.
Fun Facts about Niels Bohr:
Picture of Niels Bohr: http://bit.ly/VfJigs
Picture of Bohr's atomic model: http://bit.ly/OM0DKb Information about Ernest Rutherford:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 117.
Fun Facts about Ernest Rutherford: http://bit.ly/PEF0wC
Picture of Ernest Rutherford: http://bit.ly/QuW4SX
Picture of Rutherford's atomic model: http://bit.ly/S6oWlS
Picture of gold foil experiment: http://bit.ly/TyOWnc
Video of gold foil experiment: http://bit.ly/TwKSTW Information about J.J. Thomson:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 115.
Fun Facts about J.J. Thomson:
Picture of J.J. Thomson: http://bit.ly/R6Ro7f
Picture of Thomson's atomic model: http://bit.ly/QuVEfk
Picture of cathode ray: http://bit.ly/S6nU9r Information about Aristotle:
Picture of Aristotle: http://bit.ly/RI5ysI
Information about John Dalton:
Holt Science Spectrum®: Physical Science with Earth and Space Science ©2008. Page 114.
Fun Facts about John Dalton:
Picture of John Dalton: http://bit.ly/RY21Hf What in the world are isotopes? Isotopes are atoms of the same element that have a different number of neutrons, therefore having a different atomic mass. Electrons Protons The atomic number is the number of protons in an atom. The mass number is the amount of protons added with the amount of neutrons. To get the average atomic mass you have to take the mass number of a specific isotope and the percentage (out of 100) that it is found and multiply them. Then you add the totals for all different isotopes. Protons are the particles in an atom that have a positive charge. Neutrons are the particles in an atom that have no charge. The electrons are the particles in an atom that have a negative charge. How many more protons there are than neutrons in an atom. The difference between the atomic mass and the atomic number is that the atomic number is the measure of only the protons in an atom and atomic mass is the measure of the protons and neutrons of an atom combined. These things were not all true but no one challenged them for close to 100 years because people didn't have all of the experimental technology and things they have now. How to get average atomic mass Element: Lead Isotopes:
Pb 204 206 207 208 Multiply the mass of the isotope by the percentage of how often you find it. 203.9730 x 1.4% 205.9744 x 24.1% 206.9759 x 22.1% 207.9766 x 52.4% = 2.856 = 49.6398 = 45.7417 = 108.9797 Average atomic mass of lead: 207.2172 1913 A.D. 1932 A.D.
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