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Volume 1

Issue 3

November, 2013


Discovery of the Neutron James Chadwick

Brock Larsen & Zoe wissler

ChadwiCk’s disCoveries: James Chadwick realized their must be more to an Atom then protons and electrons because the atiomic number was less then the atomic mass this questions this idea to a series of expierments where he traced partical radiation and determined there was another Componet to atom’s; the nuetron. When testing and expierementing Chadwick used testing and complex mathematical calculations to prove his claim that there was more to atoms then protons and elctrons making them legitamite.

Significance of his discoveries:

James Chadwick won the Nobel Prize Award in physics in 1935 for the discovery of the Neutron

Understanfding all components of the atom helps us understand elements and how they are made up. When lookind at the periodic tbable, the mass number of a element is found by adding the number of protons and neutorns. We are able to unerstand Isotopes when looking at neutrins beacause neutrons is what

they

differ

in.

Knowing

everything inside the atom made them

then

ever

it a more clear understanding of before. The model of an atom is an on

going process and the discovery of the neutron enhanced the model by adding neutrons to the nucleus.

Impacts of the Neutron: The discovery of the neutron led to many advancements in nucleur science. The understanding of the neutron is the reason fot the creation of nucleur power and the atomice bomb, both of whuch impacted the wrold greatly.


Christina Nguyen & Vinh Banh

Who’s J.J Thomson? Sir Joseph John Thomson was born in Cheetham Hill, Manchester, United Kingdom on December 18, 1856. Thomson was known as a British physicist and in 1897 he discovered the electron (Plum Pudding Model.) Not only is Thomson credited for his findings of electrons within atoms he was also credited for finding the first evidence for isotopes of a nonradioactive element in the year of 1913. Isotopes are atoms with the same number of protons but different in neutrons, therefore it changes the atomic mass. In 1906, Nobel Prize Physics was awarded to J.J Thomson for his discovery of the electron and he was also awarded for the conduction of electricity in gases.

What was the discovery of the Plum Pudding Model? In 1897, an experiment conducted by J.J Thomson was done, and to his findings he discovered that within an atom there were particles called “electrons.” Electrons are known to be a negatively charged particle. He conducted his experiment by shooting a cathode-ray through a tube. He found out that inside the atom not only were there electrons but there were also protons. The title “Plum Pudding” came from this experiment; the protons were considered as the pudding, while the electrons were plums. The picture on the left shows that in an atom there are positively charged particles that is considered as the pudding in this case, and the electrons are round dots representing plums. The medium circle is representing an atom that is forming a positive ion and not a negative ion. It’s not forming a negative ion because it had loss one electron (plum) therefore there are more positive charges making it a positive ion. The smaller picture shows that an electron and going from one atom to another to present the conduction of electricity.

Why was the Plum Pudding Model Important? The Plum Pudding Model was important because it determines an elements amount of electrons that are attracted to the nucleus. Without the plum pudding model the periodic table would be organized differently because we’d have a different style of electron configurations. We’d probably not discover some of the elements on the periodic table without it, and without some of the elements we’d skip atomic numbers. We’d probably have different atomic numbers and be disorganized and not know the amount of actual protons, neutrons, and electrons. The plum pudding model also describes how elements have positive and negative charges.


KA-BOOM! The Neutron James Chadwick This Nobel Prize winner for Physics eternally changed the world. He discovered the neutron in 1932. This discovery made possible much advancement in the field of science such as the creation of the atomic bomb or the Manhattan Project. Also since isotopes depend on the number of neutrons in an atom, they would not exist without Chadwick’s discovery.

Figure 1

Chadwick’s Experiment One day in Chadwick’s lab, he and his colleges were experimenting with alpha particles and certain elements from the periodic table. They shot the alpha particles (helium atoms) at Boron, Beryllium, and Lithium. As you can see in figure one, radiation waves are produced. They found that the radiation waves they produced had no charge; they could not be protons or electrons. What could they be? After pondering this for a short time, they decided to put the zero charged radiation waves through paraffin (wax). WOW! Out shot protons! What was making them go so fast? It was neutrons!

Figure 2

Criticism Good Things that came out of his Experiment: • He found the last subatomic particle. • Neutron (radiation) therapy helps with cancer. • Nuclear Power Plants • Figured out atomic mass issue. Able to use atomic number to solve. Bad Things that came out of his Experiment: • Ability to mediate a Nuclear Chain Reactor. Which eventually lead to the Atomic Bomb. • His model was incorrectly shaped. It is to be more cloud-like and circular. The discovery of the neutron has its ups and downs. An up side being it helps treat cancer and fuels nuclear power plants. A down side is it has killed thousands of people. It has its life saving qualities and its destructive qualities. By Colby Williams and Paden Sheumaker


Ernest Rutherford During Rutherford’s career as an atomic physicist he performed experiments with alpha particles, and through these he experiments in 1911 he discovered the nucleus. His famous gold foil experiment is what he used to prove the existence of the nucleus and that atoms are mostly empty space.

Hypothesis His hypothesis going into this experiment was that atoms are composed of mostly empty space and that most of the particles would pass through the gold foil.

Process His apparatus which is a lead cube with a source of alpha particles that has a hole that allows him to accurately direct alpha particles. He directed these alpha particles at a sheet of gold foil at a perpendicular angle. In a semi-circle around the foil was a zinc sulfide screen that would allow them to see the particles that struck the screen. To adjust the eyes of the person who would be observing the particles strike the screen. About 1 in every 20,000 particles would deflect at about 90 degrees.

Critique While the chances for this are slim do to the large gap between the two numbers the chance for human error is still present as the means for counting the number of times and where the partials were reflected or diffracted was a person in a dark room. Apparatus-the technical equipment or machinery needed for a particular activity or purpose Alpha particles-a helium nucleus emitted by some radioactive substances, originally regarded as a ray.


By Malachi Canada, Nov. 2013

Three Heads are Better than 1 The Three GODS of the ATOM Who came up with the Electron Cloud Model? It’s very hard to point a finger on which one of these three brilliant scientists came up with this Cloud theory as, All three of these scientists had a very important part and say in this specific Electron Model. Ernest Rutherford discovered that the Atom is mainly an empty space with a tiny but very heavy nucleus. But on the other hand Bohr also had a model of atomic structure in where electrons orbited the nucleus in a circular motion. But that theory was not right, because orbits are not even close to circular at all. But he had the right idea as electrons were moving around in the nucleus which was the only thing right about his theory. But the most important of the three was Werner Heisenberg was really the person that determined that the only right way to find the location of electrons is as a probability distribution, and this led to the idea of an Electron Cloud where you can only talk about the relative probability of find an electron in a certain volume. When was the Electron Model first created? It was about a little more than 100 years that this model was created and was a correct theory . The electron cloud model was invented throughout the 20th century. (1900's} Yet after Neils Bohrs model in 1913. This was around the time the three scientists put together all their theories. But then the two other scientists added on to this theory. It was developed in 1925 by Erwin Schrodinger and Werner Heisenberg. This model provides the means of visualizing the positions of electrons in an atom. What led to these three scientists coming up with such a brilliant model? Because it was a way to describe where electrons are going and when they get around the nucleus of an atom. Also Chemists can use the electron cloud model to assign electrons to different atomic orbitals. these orbitals. not all of them are spheres. Atomic orbitals also explain the patterns in the periodic table. 4 Main And Important Facts about The Electron Cloud Model. 1. Electrons occupy only certain orbits around the nucleus. Those orbits are stable and are called "stationary" orbits. 2. Each orbit has an energy associated with it. The orbit nearest the nucleus has an energy of E1, the next orbit E2, etc. 3. Energy is absorbed when an electron jumps from a lower orbit to a higher one and energy is emitted when an electron falls from a higher orbit to a lower orbit. 4. The energy and frequency of light emitted or absorbed can be calculated by using the difference between the two orbital energies.


By Mario Cruz, November 2013

James Chadwick made the discovery of the Neutron in 1932.

Why yes, he did succeed. He succeeded in finding out that a neutron had about 0.1 percent MORE mass than the protons. His findings were all written in his first paper ‘Possible existence of neutron’. He later earned the noble prize in 1935 for this discovery. Picture A

He went to school in Manchester, England. He graduated from the Honours School of Physics in 1911 and started working under the famous Ernest Rutherford (who is known for discovering the nucleus) for about two years before WWI. After the war he returned to England and began working with Rutherford -who at this point- was studying, along with others, Atomic Disintegration.

Picture B Well while they were doing this study, they saw that the atomic number was less than the atomic mass of an element. For example, the element helium had an atomic mass of 4, where as the atomic number was only 2. They knew that electrons had almost no mass so it had to have been something else added to the protons to make the atomic mass. Now get this! It was at this point that Rutherford gave the idea that maybe; just maybe, there was a particle with mass but without a charge. Now this seems very logical because if you just add more electrons to the protons until it equals that atomic mass it would conflict with what element is being portrayed and would; essentially, mess up the way the whole periodic is set up.

Neutron- sub Atomic particle located in the nucleus of an atom that has no charge Nucleus- very dense region, located in the center of an atom, consisting of protons and neutrons

You see, when Rutherford stated his idea, it was in the back of James Chadwick’s mind the whole time he was doing work on other experiments and such. An experiment that Frederic and Irene Joliot-Curie did caught Chadwick’s eye, because this experiment consisted of a different method for tracking particle radiation. Chadwick repeated many of their experiments, but his goal was not to track its electromagnetic spectrum; instead, his priority was to look for a neutral particle. Pictures A and B are diagrams of what the experiment looked like. Picture A is in Advanced Chemistry Terms and Picture B is in Simple Basic Chemistry Terms.

Atomic Disintegration- the process resulting in the change of a radioactive nucleus. Atomic Number- equivalent to the number of protons in the nucleus Atomic Mass- average mass of an atom (number of protons plus the number of neutrons) Element- a substance consisting of one type of atom Electrons- negatively charged particles Protons- positively charged particles


Tanner Peeler & Rayvon Gray November, 2013

James Chadwick a scientist in 1932 discovered an important piece of scientific information, the neutron. He discovered the neutron during various experiments with different elements (from the periodic table) with various atomic numbers. Chadwick’s inspiration to discover the neutron was JJ Thomson, Ernest Rutherford, and Niels Bohr’s recent research of the proton, nucleus and electron configuration.

Chadwick experiment was very unique of how he went about it. He took recent scientific experiments and made small changes to make his experiment more accurate. His experiment consisted of shooting alpha ions through paraffin wax and watched the protons bounce back and the neutrons go through. Since the neutrons are either positive or negative charge they went straight through the wax.

Although his experiment proved to be extremely accurate, there were faults to his experiment. He did very good work but did not document very well. There were gaps in his notes. Having said that, he did prove all his work mathematically. Our view of Chadwick’s experiment is that he helped develop scientific evidence for more research to be done. He unintentionally led other scientists to work off of his work and go more in depth with his data.


Around and Around it Goes

Taylor Bush and Mary Pham

November, 2013

Niels Bohr was a Danish physicist who contributed greatly to the discoveries of the atom. He came up with a revolutionary theory on atomic structures. Bohr won the 1922 Nobel Prize in physics. His own research led him to theorize in a series of articles that atoms give off electromagnetic radiation as a result of electrons jumping to different orbit levels, departing from a previously held model by Ernest Rutherford. Though Bohr’s discovery would eventually be changed by later scientists, his ideas formed the basis of future atomic research. Around 1910, Bohr came up with his model, and in this model it shows that he came to the conclusion of: • •

Protons and neutrons occupy the nucleus of an atom Electrons travel in the orbits

Ernest Rutherford came up with his own model previous to Bohr and, though the two models are similar, they have their differences as well. Rutherford had shown that the atom consisted of a positively charged nucleus, with negatively charged electrons in orbit around it. Bohr expanded upon this theory by proposing that electrons travel only in certain successively larger orbits. He suggested that the outer orbits could hold more electrons than the inner ones and that the outer ones determine the atom’s chemical properties. Although there are many correct pieces to Bohr’s atomic model, there are some incorrect pieces too. Such as:    

The Bohr Model provides an incorrect value for the ground state orbital angular momentum. It makes poor predictions regarding the spectra of larger atoms. It does not predict the relative intensities of spectral lines. The Bohr Model does not explain fine structure and hyperfine structure in spectral lines.

This model is important because it better describes the structure of the tiny particles we call atoms. Of particular importance is the idea that electrons move around the nucleus in orbitals. Vocabulary:  Electron: negatively charged subatomic particle in an atom  Proton: positively charged subatomic particle in the nucleus  Neutron: subatomic particle with no charge in the nucleus  Nucleus: dense center of an atom


By Cassie Handley and Marissa Van Elsen November 2013

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J.J. Thomson found that atoms have electrons in them which are negatively

charged. Thomson had made an experiment around the early 1900’s to figure this out. Other scientist had been working on the idea but hadn’t really did an experiment, and finally Thomson did. Thomson put electrically charged plates and magnets in a high-vacuum cathode-ray tube that numerous scientists had been using at the time to study electric discharge. (See diagram). This discovery helped the world of chemistry a lot. If Thomson didn’t find out about the electrons we wouldn’t know how atoms were made or about electron configurations because those have to with electrons. Even though Thomson found out that atoms have electrons, Thomson didn’t have the technology we have today so any slightest mistake could have never discovered the electron. Also, the guesses he made while doing the experiment could have been wrong and completely ruin the experiment.


WHERE IT ALL STARTED:

by Kerrigan Torres November, 2013

At the age of 19, Rutherford atteneded the University of New Zealand and became a student of J.J. Thomsons. Thomson is known for the Plum Pudding model, he proposed that the atom was composed of electricity, which was had a positively charge fluid “Pudding” that helped balance out the electrons that were scattered around inside “Plums”. Although Thomson had claimed all of this to be correct there was no way he could explain certain wavelength patters. RUTHERFORD’S DISCOVERY: Rutherford saw the holes missing in the Plum Pudding model and went into deeper experiments; In March of 1911 Rutherford announced the nuclear model of the Atom. His experiment consisted of a beam of alpha particles aimed at a thin sheet of gold paper, as a result most passed through without deflection, and others were deflected in different angles. This experiment could only be understood when the gold atoms had a big nucleus. Although Rutherford’s experiment wasn’t consistent all of the time, the holes in it helped scientist such as Bohr, Chadwick, and Heisenberg increase scientific models later in life. HOW IT CHANGED SOCIETY: Rutherford’s Experient help shaped the Science we have today, without his discovery we might not have the same knowledge or advancements.


Leilla Memisevic & Ajla Selimovic November 2013 Picture a plum pudding. What does it look like? Fruit cake with raisins scattered everywhere, right? As you’re reading this article, keep picturing that plum pudding, as it will further your understanding on the atomic model theory, found by Thomson in 1904. A great scientist and a physics mentor, Sir Joseph John Thomson had a tremendous impact on the world with his discovery of the electron, a true advancement in understanding the atom beyond its structure and look. Otherwise, how would we answer questions concerning the positive and negative charges of an atom? To this day, that portion of Thomson’s model. In 1897, Thomson used a high-vacuum cathode-ray tube ( shown in figure 1) to discover the electron. By placing two electric plates in a cathode tube (one positively charged and one negatively charged), he saw that the ray travelling in a straight line deflected. Thomson noticed that the glowing light inside the tube were smaller particles with a negative charge that would deflect when electric or magnetic fields were applied, thus explaining the discovery of the electron. Thomson assumed the model to be sphere-like with positive matter containing electrons distributed to positions according to electrostatic forces (shown in figure 2). Referring back to the first paragraph, this model relates to the dispersion of raisins in a pudding’s soft crust. This explains why Thomson’s atomic model is called the “plum pudding model”. About five years later, another physicist named Ernest Rutherford experimented with gold foil, a particle emitter and a detecting screen to disprove Thomson’s theory. As the majority of the alpha particles passed through the gold foil, a rare one would deflect. The only logical explanation for the deflection was that the positive charge in the atom was not distributed the way Thomson theorized it to be. The plum pudding model theory was abandoned in favor of Rutherford after discovering that electrons orbit around a small, dense concentration of mass called the nucleus, another famous discovery of Rutherford. Without Thomson’s discovery, the negatively charged particles in an atom would remain unidentified. The advanced understanding that Thomson has provided the world with allows us to conduct many experiments, make calculations to answer questions about elements and help scientists improve the atomic model. His determination on the negatively charged particles led to the development of the mass spectrograph, which was able to discover isotopes in a large number of radioactive elements. The knowledge of electrons explains chemical reactions and it brings innovation to the table for many science departments. It leads to more and more discoveries, advancing our understanding on the atom EVEN MORE! All in all, we wouldn’t have gotten this far with the atomic model without Thomson. His work was simple, yet very significant in the history of chemistry. His plum pudding model theory may not have been a success, but his discovery of the electron brings new ideas and creations for chemists experimenting new things all over the world. We would be clueless about atoms if it weren’t for Thomson. Let’s just say Thomson’s curiosity unlocked the greatest mystery of the most important and fundamental part of the atom.


Randy Nguyen

November, 2013

The Gold Foil Experiment Rutherford conducted an experiment in 1909 called The Gold Foil Experiment. He shot alpha particles (an atom with 2 protons and 2 neutrons) at a sheet of gold foil 1/3000inch thick and tracked the particles. The particles went through the gold foil and flied off into different directions, but some bounced back. Rutherford found that an atom must have a nucleus 10,000 times smaller than the atom and the nucleus is where the positive charge and mass is. The discovery of the neutron hasn’t happened yet so he thought that the nucleus is full of just protons. His discovery is that the negative charge electrons rotate around the positive charge protons in the nucleus like planets rotating around the sun. He received the Nobel Prize in Chemical in 1908 for his discovery. Energy Levels Bohr found that the electrons that rotate around a nucleus go into energy levels. He did this using the Rydberg Formula. He found that some levels can only fit a certain number of electrons. The first level can only fit 2 electrons, the second and third can only fit 8 electrons and the fourth can only fit 14 electrons. There’s more but I don’t want to name them. The amount of levels is a way the periodic table is organizes. The lower elements on the periodic table have more levels. He also received the Nobel Prize in Chemical in 1922 for his discovery. Credit Both of them got a Nobel Prize for their discovery but who should get the credit. Their discoveries are both apart of the planetary models. Rutherford found that the atom is like the solar system which is why it’s called planetary. But Bohr was the one that improve Rutherford’s model. Some say both should get credit but that’s taking the easy way out. Who do you think should get the credit?


T.J. McIntosh and Cameron McIntosh

Electron Cloud Model This model was created by Neils Bohr and Werner Heisenberg, then developed in 1925 by Erwin Schrodinger. The model pretty much helps us to state that we can’t exactly know where an electron of an atom is but they are more likely to be inspecific areas. In the shells there are repeating patterns which makes the atom the element or gives it its chemical properties. Bohr’s understanding of the atom allowed him to help creat the atomic bomb in Germany. How did he come up with his theory though? He shot large charge particals at thing gold foil some went right through the foil. But others went to a different angles or other ways. He concluded that the atom was mostly empty space.But there was a dense central mass (nuclues) that the alpha particals can’t pass through. Schrodinger improved on their model and came up with an equation that proved that you can never really truly prove the exact orbit of the electrons. Which created the electron cloud. Through Rutherfords and Bohr model is flawed it’s still used to give people the understanding of the atomic structure and because it’s very easy to understand. The equation Schrodinger came up with was H I=E I.

Erwin Schrodinger

Werner Heisenberg

Niels Bohr


Who He Was

by Thien Truong & Enrique Lopez Nov. 2013

Joseph John Thomson was born in Chatham Hill on December 18, 1856. Thomson was enrolled at Owens College in 1870 and in 1876 he entered Trinity College. Thomson became a lecturer in 1883 and master in 1918. He then was a Professor of Experimental Physics at Cambridge. JJ Thomson was interested in the structure of atoms. He won an Adam Prize in 1884 on Treatise on the Motion of Vortex Rings.

What He Found JJ Thomson discovered the electron in 1897 after doing a series of lab experiments. He used a cathode ray tube to study the nature of electric discharge of light rays. Many others were attempting this experiment as well but what he did different is that he sucked out the gasses from the cathode ray tube crating a vacuum so there would be no interference. He had electrically charged plates and magnets around the tube and when he turned it on the light would deflect. Through repeated trials he came to the conclusion with the experiment as evidence that “bodies much smaller than atoms” were present in the atom. He then calculated them as having a high charge-to-mass ratio. In 1904 he came up with the plum pudding atomic model as the structure of the atom. He suggested that the atom was a sphere of positive matter in which electrons are positioned by electrostatic forces. He later tried to estimate the number of electrons in an atom from measuring the scattering of light, x, beta, and gamma rays which initiated the research that Ernest Rutherford, his student, used to come up with the planetary atomic model.

Argument Although JJ Thomson’s atomic model was adopted into the science community, it was just a few years later that his idea was disproven and a new model, constructed by one of his own students, was adopted. The experiment that he used to find the electron was also being used by other fellow scientist. What he did differently was that he shot the ray of light through a vacuum instead of filling it with gasses that interfered with the experiment. This was a good experiment and because of the important discovery of the electron, the atomic science world was completely changed. As the electron was the first known subatomic particle, new ideas were created. Now we have found all the way to an even smaller particle, the Higgs Boson. The electron is very important as it is what goes through our power line and was an important factor in the development of TVs and computer screens. He came up with the idea for the plum pudding model because John Dalton had previously concluded that atoms were spheres so he went upon to embed those electrons and because no evidence proved otherwise the model was kept.


List of Sources http://en.wikipedia.org/wiki/Plum_pudding_model http://images.yourdictionary.com/cathode-ray-tube abyss.uoregon.edu/~js/21st_century_science/lectures/lec11/html www.nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-bio.html www.chemheritage.org/discover/online-resources/chemistry-inhistory/themes/atomic-and-nuclear-structure/thomson.aspx http://socratic.org/chemistry http://library.thinkquest.org/C001124/gather/aexp.html http://ansnuclearcafe.org/2011/10/19/pioneers102011/ abyss.uoregon.edu/~js/ast123/lectures/lec04.html www.iun.edu/~cpanhd/.../modern-atomic-theory/rutherford-model.html Prentice Hall Chemistry Text Book (pg. 119-121) http://physics.bgsu.edu/~stoner/P202/atoms/sld006.htm http://chemwiki.ucdavis.edu/Physical_Chemistry/Quantum_Mechanics/Quantu m_Theory/Trapped_Particles/Atoms/The_Bohr_Atom http://www.pbs.org/wgbh/aso/databank/entries/dp13at.html http://www.bbc.co.uk/manchester/content/articles/2008/09/10/100908_ruther ford_physics_feature.shtml http://www.rsc.org/chemsoc/timeline/pages/1911.html http://chemwiki.ucdavis.edu/Inorganic_Chemistry/Electronic_Configurations "Chemical Structure." PicHost. N.p., n.d. Web. 05 Nov. 2013. Images, Getty. "Illustration of Thomson's 'Plum Pudding' Model of Poster." Illustration of Thomson's 'Plum Pudding' Model of Poster. N.p., n.d. Web. 03 Nov. 2013. "J.J. Thomson - Biographical." Nobelprize.org. Nobel Media AB 2013, n.d. Web. 05 Nov. 2013. "Joseph John Thomson." Homepage of the Chemical Heritage Foundation. N.p., n.d. Web. 04 Nov. 2013. Ouellette, Jennifer. "Don’t Be Dissin’ the Bohr Model." Cocktail Party Physics, Scientific American Blog Network. N.p., n.d. Web. 03 Nov. 2013. "Plum Pudding Model Pictures." Plum Pudding Model Pictures, Plum Pudding Model Image, Science&Technology Photo Gallery. N.p., n.d. Web. 03 Nov. 2013. Strassler, Matt. "Electrons: On the Outskirts Of Atoms." Of Particular Significance. N.p., 21 Jan. 2013. Web. 05 Nov. 2013


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