Understanding Neutrality in Alpha/Beta Decay

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In Summary, alpha decay (the emission of helium nuclei) leaves behind a nucleus with an increased number of protons, but the number of electrons remains the same. Beta decay (the emission of electrons) does not change the number of protons in the nucleus, but the number of electrons changes.
  • #1
troy611
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I have the following confusion:

In an alpha or beta decay, there's a change in the nucleus, i.e. there's a change in number of protons and neutrons, but there's no change in the number of electrons. So, how is it that the product is neutral?

To make this more clear,

Suppose U-238 (with 92 protons, 92 electrons, 146 neutrons) decays(alpha decay, i.e. helium nuclei is emitted) into Th-234 (90 protons, 144 neutrons). The confusion is: to be neutral, Th formed should have 90 electrons, but there are 92 electrons to start with...what happens to the other 2 electrons?

This applies to other decays as well...thank u for any help
 
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  • #2
troy611 said:
Suppose U-238 (with 92 protons, 92 electrons, 146 neutrons) decays(alpha decay, i.e. helium nuclei is emitted) into Th-234 (90 protons, 144 neutrons). The confusion is: to be neutral, Th formed should have 90 electrons, but there are 92 electrons to start with...what happens to the other 2 electrons?
If this were in metallic U-238, the alpha particle would stop, find two electrons, and become a helium atom. Simultaneously, the Th-234 would release the two extra electrons it doesn't want. If this were in an insulator, there may be dislocations (charge centers), because the helium atom will be displaced from the Th-234..

Bob S
 
  • #3
troy611 said:
Suppose U-238 (with 92 protons, 92 electrons, 146 neutrons) decays(alpha decay, i.e. helium nuclei is emitted) into Th-234 (90 protons, 144 neutrons). The confusion is: to be neutral, Th formed should have 90 electrons, but there are 92 electrons to start with...what happens to the other 2 electrons?

No electrons were created or destroyed. You had 92 electrons to start with, and there are still 92 electrons somewhere.
 
  • #4
@Bob S...so you mean in this particular decay, no alpha particles are formed?
@bcrowell...they can't be destroyed, but that is my question, they are somewhere, but where are they?
 
  • #5
troy611 said:
@Bob S...so you mean in this particular decay, no alpha particles are formed?
In this type of decay, alpha particles certainly are formed, and they move a few (or tens or hundreds) of microns before they stop. Of all the elements, helium (of which the alpha particle is the nucleus) has the highest ionization energy (~ 24 eV) and so the helium ion has the highest affinity for grabbing electrons. When the alpha particle stops, it will steal two electrons from the U-238 and become a helium molecule in the U-238.

Bob S
 
  • #6
ok...now i understood it regarding alpha decay

but what about beta decay?

for example,
P (17 neutrons, 15 protons, 15 electrons) beta(-) decays into S (16 neutrons, 16 protons).
1 electron, 1 proton(which stays in the nucleus), and 1 anti neutrino are formed. In my textbooks and all, its given that the electron formed escapes.

now, for neutrality, S should have 16 electrons, but the atom has only 15 electrons(the one electron formed has escaped), does that mean the S atom formed is positively charged?

ps: i m sorry, it may be becoming boring for u...but i really have this confusion...thanx for helping out on the alpha decay.
 
  • #7
When a beta particle escapes a nucleus (n -> p), then the charge increases from Z to Z+1, e.g., P(Z=15) to S(Z=16). The beta particle escapes that nucleus/atom, but it does not travel far. May be mms' or cm's. Meanwhile, the Z+1 nucleus attracts an electron, and then there is a cascade of electrons transferred until somewhere the beta particle (an electron) is captured by an ion and becomes a neutralized atom.
 

Related to Understanding Neutrality in Alpha/Beta Decay

1. What is the difference between alpha and beta decay?

Alpha decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (consisting of two protons and two neutrons) from its nucleus. Beta decay, on the other hand, is a type of radioactive decay in which an atomic nucleus emits a beta particle (either an electron or a positron) from its nucleus.

2. How does alpha decay occur?

In alpha decay, the nucleus of an atom becomes unstable due to an excess of protons or neutrons, causing it to emit an alpha particle. This process is spontaneous and occurs in heavy, unstable nuclei in order to achieve a more stable state.

3. What is the role of neutrinos in alpha and beta decay?

Neutrinos are subatomic particles that are emitted during beta decay. In beta minus decay (β-), a neutron in the nucleus is converted into a proton, an electron and a neutrino. In beta plus decay (β+), a proton in the nucleus is converted into a neutron, a positron and a neutrino.

4. What is the significance of understanding neutrality in alpha/beta decay?

Understanding neutrinos in alpha and beta decay is important for studying and predicting the behavior of radioactive elements. It also helps scientists to better understand the fundamental forces and interactions within the nucleus of an atom.

5. How is the rate of alpha and beta decay determined?

The rate of alpha and beta decay is determined by the half-life of the element, which is the amount of time it takes for half of the atoms in a sample to decay. This rate can be affected by factors such as temperature, pressure, and the presence of other elements.

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