Thursday, October 7, 2010

The Discovery of Neutrons

Important Definitions:
Neutron: an elementary particle with 0 charge and mass about equal to a proton; enters into the structure of the atomic nucleus.  
Electron: an elementary particle with a negative charge equal to the positive charge of an electron.
Proton: an elementary particle with a positive charge equal to the negative charge of an electron.
Quark: any group of six elementary particles having electric charges of a magnitude one-third or two-thirds that of the electron.
Alpha particle: a positively charged particle, indistinguishable from a helium atom nucleus and consisting of two protons and two neutrons.
Isotope: one of two or more atoms with the same atomic number but with different numbers of neutrons.
Beta decay: radioactive decay of an atomic nucleua that is accompanied by the emmision of a beta particle.
Beta particle: a high-speed electron emitted in the decay of a radioactive isotope.
Polonium: a radioactive metallic element that has simillar qualities as bismuth.

What is a Neutron?
A neutron is a tiny suatomic particle that can be found in almost all forms of matter (3). The only stable exception where a neutron is not found is in a hydrogen atom (3).The neutron is located in the atomic nucleus, and it is bound with protons through a strong nuclear force (3). The term "neutron" is used because it has no electrical charge and is therefore neutral (3). A neutron is the result of the combination of a proton and an electron (3). Because a proton has a positive charge equal to the negative charge of an electron, the two are attracted to each other and together they form a neutron (3). Most atoms have an equal number of protons and neutrons in their nucleus (3). However, when this balance is broken, the atom becomes an isotope (3). Neutrons can survive ouside of the nucleus for about 15 minutes, before they undergo beta decay and break down into protons and electrons (3).
Neutrons vs. Protons
Slightly lesser masses than neutrons (2).
Composed of two up quarks and one down quark (2).  
Extremely stable outside the nucleus; takes a long time to decay (2).
Discovered by Ernest Rutherford in 1919 (2).
Used to treat cancer (2).

Slightly greater masses than protons (2).
Composed of two down quarks and one up quark (2).
Extremely unstable outside the nucleus; decay within 15 minutes (2).
Discovered by James Chadwick in 1932 (2).
Used to create weapons of mass destruction (2).

The Discovery of the Neutron
In 1920, Ernest Rutherford had suggested the idea of an electrically neutral particicle when he was trying to explain for isotopes of hydrogen (4). In 1930, Charles Chadwick performed an experiment that would lead to the discovery of neutrons (4). When alpha rays emitted from polonium were fired at light nuclei, the alpha rays gave rise to the penetrating rays and no electric charge could be found (4). The "penetrating rays" were considered gamma rays (4). When a beryllium target was used instead, the rays were even more penetrating than when other targets were used (4). Chadwick was able to conclude that the mysterious radiations did not have any electric charge because it was not affected by how close it was to a magnetic field (5). Gamma radiation involved the photoelectric effect, and these rays did not, so these rays could not possibly be gamma rays (5). The photoelectric effect occurs when protons stike certain surfaces and produce electrons (5). Instead of doing this, the mysterious rays discharged protons (5). This fact also proved that the particles had greate masses than chemists had formerly thought they did (5). In 1931, Chadwick proposed the thought that the neutral rays were concrete evidence of the idea that neutrons existed (4). James Chadwick received the Noble Prize in 1935 for his discovery of the neutron (5).

Affects of the Neutron
The discovery of the neutron changed subatomic physics forever and allowed scientists to discover new elements (4). It also led the discovery of nuclear fission and is used to create nuclear weapons (4). Charles Chadwick was the leader of the British technical team during World War II, and he helped the U.S. invent the atomic bomb (4). The U.S. used this nuclear weapon to attack Hiroshima and Nagasaki, Japan and to defeat Japan in World War II (4).

Characteristics of Neutrons
-Subatomic particles found in nucleus of atoms, along with protons (1).
-No electrical charge (1).
-Mass = 1.6749 X 10 ^-27 kg, or 1,840 times the mass of an electron (1).
-Consists of three quarks: one up quark and two down quarks (1).
-Only stable when bound in atomic nucleus (6).
-Lifetime of free neutron is 886 approximately seconds (6).
-Only neutral to outside; have inner structure with distribution of + and - charges (6).
-Has a spin, or an inner angular momentum (6).
-Can adjust its spin in magnetic field (6).
-Can pass through massive layers with thickness of several centimeters (6).
-Can induce nuclear reactions (6).

Works Cited
(1) Wolfe, Kari. Characteristics of a Neutron. eHow Inc., 1999. Web. 07 Oct. 2010. <>

(2) Weiner, Stephen. Protons vs. Neutrons. eHow Inc., 1999. Web. 07 Oct. 2010. <>

(3) Anissimov, Michael. What is a Neutron? Conjecture Corporation, 1999. Web. 07 Oct. 2010. <>

(4) James Chadwick. Creative Commons Attribution, 2008. Web. 07 Oct. 2010. <>

(5) McPhee, Isaac M. The Discovery of the Neutron. Isaac M. McPhee, 2008. Web. 07 Oct. 2010. <>

(6) Properties of Neutrons. Frank Laboratory of Neutron Physics, 2008. Web. 07 Oct. 2010. <<>


  1. Hi Morgan! Your blog is very well put together and organized. Defining the key terms at the very beginning was a good idea and it was extremely helpful while reading your blog. However, I think the blog might have been a little bit more helpful if there were more pictures or diagrams of the experiment on the actual blog itself for reference while reading the information. Overall, I really enjoyed you blog and it was one of the few neutron blogs, which made it even more interesting!

  2. Well done! I thought the information you gathered was very informative and and the way you organized your information was great! I liked how you clearly stated what you were going to discuss in the paragraph, and the definitions at the very beginning were extremely helpful. That was a great idea! A few things i would add would be some pictures or videos to allow a visual explanation as well. Besides adding a couple of pictures, there was not much improvement needed on your blog. Great Job!

  3. Morgan I really enjoyed your presentation on the discovery of neutrons. Defining key terms at the beginning of any project is ALWAYS a great idea and helpful to the reader. It sets up a solid basis by making sure everyone is on the same page before getting into more complicated information. You did that really well and I love how you introduced your topic. In your actual presentation part of the posting I enjoyed how well organzied you were. I could easily follow and understand what you were saying. I would maybe have liked to have seen a diagram or a few more pictures to illustrate the example a little better but with your descriptive information it is not need as much. You did a great job with your detailed information. I really loved the blog posting! Keep up the awesome work :)

  4. Hi Morgan! I really love your blog! The beginning of your blog was really helpful! It helped me remember what we talked about in class and plus there was some key terms that i didnt know! I would suggest adding some pictures or videos to further explain your topic. But besides that, your blog is really organized and full of lots of helpful information! It went deeper than we did in class, so I understand this experiment more than i did before! Great job! (: