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Name: Craig
Status: student
Grade: 9-12
Location: GA
Country: USA
Date: N/A 


Question:
In our chemistry class, we stumbled upon a question which we could not answer. Since a neutron is a neutral particle with no net charge, how can a neutron be formed from a proton that splits during positron emission? Also, how could a proton gain more mass by splitting to form a neutron after emitting positive particles?



Replies:
Craig,

There are many situations where particles can change into other particles. We do not know why the universe works by the rules that scientists find, but we do know what some of these rules appear to be. Let us look at the change. First, there is a neutron. After the event, there is a proton, an electron, and an anti-neutrino. The anti-neutrino is sometimes forgotten because neutrinos and anti-neutrinos seldom react with anything. A neutrino can pass through the Earth without interacting with anything along the way, without even slowing down.

--The total charge in a particle conversion, in any interaction, must remain the same. A neutron has zero total charge. When what is called the weak force changes a neutron into a proton, an electron, and an anti-neutrino, the total charge is still zero.

--The total electron-ness must remain the same. Protons and neutrons have zero electron-ness. An electron is of course has an electron-ness of one. An anti-electron, being antimatter, has an electron-ness of negative one. The total electron-ness is still zero.

--Total energy must remain the same. The neutron has more mass than the proton. E=mc^2 is the formula for how much mass is in an object's mass. This loss of mass energy becomes electron mass energy, neutrino mass energy (which is so small that it is sometimes just called zero), and also the motion energy (often called kinetic energy) of the particles. Still, total energy stays the same.

Because these balances of the universe (and a few other more involved balances) remain the same when a neutron decays into a proton, electron, and anti-neutrino, the decay is allowed by the rules as we believe them to be.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College



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