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Beta Radiation, Mass Change
Name: Andrew
Status: educator
Grade: 6-8
Location: NH
Country: USA
Date: Summer 2012
Question:
Why does beta radiation change the mass of an isotope?
Replies:
Hi Andrew,
A beta particle(â-) is a highly energetic electron emitted from the nucleus of a radioactive atom, coincident with an antineutrino(í). Beta electrons originate from a proton of a neutron rich isotope. When a proton(2U,1D quarks, +1 charge) ejects a beta particle, it is transformed into a neutron(1U,2D quarks, neutral).
That means the original isotope has lost a proton, therefore the element has changed and gained a neutron, so the mass will remain the same. We have a change of an element and an isotope.
K40 yields â- + í and Ca40.
Hope this helps! PEHughes, Ph,D. Milford, NH
Beta particles have mass... so when they are ejected, the remaining
mass is lower. Simple conservation of mass... also, see this answer
from the Newton archives:
http://www.newton.dep.anl.gov/askasci/gen01/gen01078.htm
However, it does not change the 'mass number' (the sum of protons and
neutrons), as beta emission simply 'converts' a neutron to a proton.
The 'mass number' does not distinguish the mass of neutrons from
protons.
(there is a little more complexity to the situation, but I think this
simplification is sufficient for here).
Hope this helps,
Burr Zimmerman
Because the mass of the electron (the "beta" particle) is not in the
nucleus anymore. Neither is the mass of the anti-neutrino that also
was emitted. Also, the kinetic energy that those particles have is
no longer in the nucleus.
Tim Mooney
A “beta ray” is an electron. The nucleus of an element can gain ( or lose ) an electron, depending upon what nuclear process is taking place. In addition, this gain (or loss ) of the electron can “trigger” further nuclear processes, leading to further gain or loss of nuclear mass.
Vince Calder
Andrew
Please see this article for details:
http://en.wikipedia.org/wiki/Beta_particle
The two types of Beta radiation (particles) are electrons and positrons.
Electron rest mass from:
http://en.wikipedia.org/wiki/Electron_rest_mass
is about 9.11 x (10^(-31)) Kilograms.
Positron rest mass is approximately the same.
http://en.wikipedia.org/wiki/Positron
So beta radiation reduces the mass of the radiating substance.
Sincere regards,
Mike Stewart
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