The Discovery of a Neutron

               Today, we take for granted our knowledge of the atom. But, this knowledge is very important to our world and if it wasn't for many hardworking scientists, we wouldn't have it. In this post I will tell you about the discovery of the neutron, a neutrally-charged particle in the nucleus of an atom.

1) Ernest B. Rutherford

               In 1897 the electron with a negative charge was discovered by J.J. Thompson and it seemed to orbit around the nucleus. Later, in 1918, Ernest Rutherford made the discovery of a positively-charged proton within an atom that seemed to cancel out the negativity of the electron, creating a neutral atom. After all of these findings, many thought that this was the make-up of an atom, just the protons and electrons, because they did cancel out each other to make a neutral charge. All of this information still didn’t stop Ernest Rutherford from contemplating another part of the atom. In 1920, he theorized that there was a neutral particle in the atom with around the same mass of a proton. His reasoning for this was because of the atomic number and the atomic mass. The atomic number of an atom is the number of protons it contains while the atomic mass is the mass of the nucleus. He was finding that the atomic mass was usually greater than the atomic number, demonstrating that there was something left to discover.

 2) James Chadwick

               In 1932, a scientist by the name of James Chadwick decided to put a decade of theory to the test and prove that there really was another neutrally-charged particle in the atom. He performed tests on a new type of radiation that had been puzzling scientists for years. It was previously mistaken as “gamma rays” (a form of radiation consisting of high-radiation photons) but Chadwick was out to prove this was not true. This type of radiation was electrically neutral and was discovered in 1930, just before it was used in Chadwick’s famous experiment. The radiation seemed to be coming from the nuclei of light elements that had been exposed to other types of radiation. At this time, many scientists had been thinking that they had found new types of particles but most of them turned out to be clusters of already known particles. Because of this, many thought that Chadwick was wrong and was just dealing with the known “gamma rays” which have no mass. In order to prove them wrong, Chadwick tried to determine the new particle’s mass and if it was approximately equal to that of a proton.

              Although this thought may sound easy, it was not. A subatomic particle is not something someone can just place on the scale and weigh. But, Chadwick came up with a solution. The masses of the nuclei of many elements were already known at the time and techniques for measuring the speed of the fast-moving nucleus had already been developed. So, he decided to force the mysterious new particles into samples of selected elements. He thought that when a direct collision occurred between the new particle and the nucleus of one of the target atoms, the nucleus would be knocked out of the atom, and he would measure the velocity.

James Chadwick's Experiment

              After all of this information, you are probably thinking, why is this important? Well, the discovery of the neutron helped us to understand the make-up of the atom. The neutron actually plays a big role in the stabilization of the atom, equal to that of even a proton. Also, neutrons play an important role in the process of creating nuclear explosions and nuclear energy. This is because the bombardment of high-energy neutrons is how a scientist can split an atom. 

Works Cited:


"Chadwick Discovers the Neutron 1932." PBS: A Science Odyssey. WBGH Educational
       Foundation, 1997. Web. 3 Oct. 2010. <http://www.pbs.org/wgbh/aso/
       copyright.html>.


"Chadwick's Experiment to Discover the Neutrons." Major and Minor Worlds. N.p.,
       n.d. Web. 3 Oct. 2010. <http://library.thinkquest.org/C001124/gather/
       aexp.html>.


Crowell, Benjamin. "The Discovery of the Neutron." Lectures in Physics. N.p.,
       n.d. Web. 31 Mar. 2006. <http://www.vias.org/physics/bk2_05_05.html>.


"James Chadwick." The History of Computing Project. N.p., 21 Mar. 2010. Web. 3
       Oct. 2010. <http://www.thocp.net/biographies/chadwick_james.htm>.


McPhee, Isaac M. "The Discovery of the Neutron: James Chadwick's Remarkable
       Experiment." Suite 101. N.p., 27 Feb. 2008. Web. 2 Oct. 2010.
       <http://www.suite101.com/content/the-discovery-of-the-neutron-a46060>.


Trinh, Hoc. "James Chadwick and His Discovery of the Neutron." Helium. N.p.,
       n.d. Web. 3 Oct. 2010. <http://www.helium.com/items/
       216709-james-chadwick-and-his-discovery-of-the-neutron>.


Pictures:

1)  Ernest Rutherford. N.d. N.p., n.d. Web. 3 Oct. 2010. 
         <https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPqraesLjGdUeT6_9MM1wEDzvxqgv-J_dEpJTBjK7KKxwVL0lILhRlAOx7DP00uDL2o9MGU2Y9QsvGzd5J6J93XXM0yOTkTxqaAF-GY0UfSyCbixlcCHor9m7PKPGZLTC0gaYwIMf4LrKg/
           s320/ernest_rutherford2.jpg>.

2) Corbis, J. English Physicist James Chadwick. N.d. Wired. N.p., n.d. Web. 3 Oct. 

         2010. <http://www.wired.com/science/discoveries/news/2009/02/dayintech_0227#>.

3) Hamilton, Calvin J. James Chadwick's Experiment. N.d. Solar Views. N.p., n.d. 

        Web. 3 Oct. 2010. <http://library.thinkquest.org/C001124/gather/ 
        aexp.html>.

Video:

Discovery of Neutrons. Tutor Vista. N.p., n.d. Web. 3 Oct. 2010.
        <http://www.youtube.com/watch?v=HnmEI94URK8>.