Chadwick's Neutron Discovery
Clueless Cat: Omniscientist Onion, can you tell me more about protons?
Onion the Omniscientist: Of course. They are a very important part of an atom.
Clueless Cat: So how were they discovered?
Onion the Omniscientist: I’m getting there… you’re cluelessness is getting out of hand… Anyways, it was found through an experiment of Rutherford while he was experimenting with positive rays. Since a hydrogen atom is the simplest atom with just one proton and an electron, he ionized them to separate the nucleus from the electrons.
Clueless Cat: What's ionizing?
Onion the Omniscientist: It’s just the process of removing electrons from an atom to separate it from the nucleus. So since the hydrogen’s nucleus is consisted of a proton, the hydrogen atom was left with a proton after the ionization.
Clueless Cat: So how did the discovery of the proton help?
Onion the Omniscientist: After that, the neutron was discovered by a man named J. Chadwick. But before he could do his experiment, Rutherford had come up with a few ideas that were helpful to Chadwick’s experimentation.
Clueless Cat: What were those ideas?
Onion the Omniscientist: Rutherford thought that there were other things besides the protons in the nucleus which he temporarily called “neutral doublets.” He said that these unknown particles, which he later named neutrons, would be uncharged with a similar mass to protons.
Clueless Cat: Was there some cool experiment they used to find these neutrons?
Onion the Omniscientist: Of course! In Chadwick’s experiment, he shot alpha particles at a piece of beryllium, which produced neutrons.
Clueless Cat: How did that happen?
Onion the Omniscientist: Nuclear reactions happened between an alpha particle and a beryllium atom in the piece of beryllium to create a carbon atom and a free neutron.
Clueless Cat: Was there more to this experiment because I still don’t see how that discovered the neutron!
Onion the Omniscientist: Yes, there was more! He put some paraffin wax near the beryllium and some of the neutrons that resulted hit the wax, which released protons. (This proved that there were neutrons because at first they had mistaken the neutrons for some really strong type of gamma ray but Chadwick concluded it wasn’t possible for the photons of the gamma rays to contain so much energy.) So he inferred that it had to be neutrons because they have similar masses to protons and would have been able to push the protons out of the wax.
Clueless Cat: How did they know protons were actually coming out?
Onion the Omniscientist: Well, next to the paraffin wax was an ionization chamber which detected protons.
Clueless Cat: Oh! Wow! Sounds like a fun experiment to do.
Onion the Omniscientist: Yes, and it also gave us a lot of new information about the atomic model.
to learn about Milikan's Oil Drop Experiment!
