James Chadwick

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James Chadwick and the Neutron

It was known from before that the atom had only positively charged protons and equal negatively charged electrons that make the whole charge of the atom neutral. The atomic mass seemed to be different from the mass of the protons. Since electrons have a very small mass they are not counted in the atomic mass. For example hydrogen had 1 proton and the atomic mass was 1. Helium had 2 protons but its mass was 4 instead of 2. This is what made Sir James Chadwick puzzled. In that time they didn’t have advanced technology and therefore they were only able to detect the subatomic particles by their charges. They discovered that neutral radiations used to collide with the protons causing them to travel to the opposite way with velocities. As if something with more mass than the proton hit the proton and made it go to the opposite direction. They used to say that the neutral radiations are high energy photons that are called Gamma rays and had a neutral charge were responsible for this. But since the Gamma rays didn’t have mass James didn’t approve this. He made an experiment and discovered that subatomic particles with no charge with a mass 1% more that the proton occurred and were responsible for this. He compared the Gamma rays to a marble and the protons and neutrons to billiard ball. If you hit the marble (Gamma rays) with a billiard ball (proton) it won’t travel because of the high difference in mass. However, if you hit a billiard ball (neutron) with another billiard ball (proton) it will travel because of the almost equal masses. Finally he discovered the neutron and his findings were quickly accepted. He received a Nobel Prize in 1935 for his discovery. Done by: Abdulla Albanna Grade:10E
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