Simple doubt in nuclear fission

[Vibhor]

Hi all ,

I have a very simple doubt in the basics of radioactivity .

Nuclear fission is the splitting of the nucleus of a heavy atom such as U²³⁵₉₂ by bombarding with slow neutrons into two lighter nuclei with a simultaneous release of huge amount of energy .

Now my doubt is that -

Can a nucleus exist independently ? I mean in the nuclear fission process we talk about bombarding neutron on a heavy nucleus . But what about the electrons surrounding the nucleus ? And what about the electrons of the atoms of daughter nuclei?

So is it basically bombardment of neutron on a heavy atom or a heavy nucleus ?

I am asking this because in radioactivity we talk only about the nucleus not the atom . So what about the electrons orbiting the nucleus of atoms involved in the fission process ?

I would appreciate if someone could help me understand this .

Many Thanks .

 

[Orodruin]

We do not talk about the electrons because they are largely irrelevant for the processes in question. What is relevant is the nucleus.

 

[Vibhor]

We do not talk about the electrons because they are largely irrelevant for the processes in question. What is relevant is the nucleus.

Ok.

Please confirm these -

1) The respective electrons are orbiting the parent and daughter nuclei before and after the fission process .

2) Precisely it is the heavy atom on which the neutron is bombarded .

3) The result of fission is two daughter atoms .

Are the above statements correct ?

 

[Orodruin]

1) The respective electrons are orbiting the parent and daughter nuclei before and after the fission process .

Not necessarily.

2) Precisely it is the heavy atom on which the neutron is bombarded .

Not necessarily.

3) The result of fission is two daughter atoms .

Not necessarily.

Which is why we don't talk about the electrons. All the important physics is in regards to the nuclei.

 

[Vibhor]

Not necessarily.

If electrons are not necessarily orbiting the daughter nuclei after the fission process , then are the nuclei existing independently ?

Not necessarily.

If neutron is not bombarded on a heavy atom , and instead on a heavy nucleus then does the nuclei exist independently (without electrons orbiting it )

Not necessarily.

What is necessarily happening ? Aren't these daughter nuclei part of atoms . Again , does a nucleus exist independently (without electrons orbiting it )

Which is why we don't talk about the electrons. All the important physics is in regards to the nuclei.

OK but it is the atom on which the neutron is bombarded and not exactly the nucleus .Isn't it ?

Please elaborate .

 

[jbriggs444]

If electrons are not necessarily orbiting the daughter nuclei after the fission process , then are the nuclei existing independently ?

If one has a daughter nucleus moving away from the fission location at high speed, it is likely to ionize at least partially, losing (or gaining?) one or more electrons in the process. How the electrons associated with the parent nucleus are divided between the daughter nuclei is irrelevant to the fission process.

If neutron is not bombarded on a heavy atom , and instead on a heavy nucleus then does the nuclei exist independently (without electrons orbiting it )

[It's "does the nucleus" or "do the nuclei"]

There is nothing that stops you from bombarding a [partially] ionized Uranium plasma with neutrons if you want to. But it is usually more convenient to bombard a chunk of metallic Uranium. If you bombard a chunk of metallic Uranium, it is tough to hit a nucleus without having hit an "atom".

But it's also irrelevant. Neutrons are neutral. They pass through electron clouds without interaction.

OK but it is the atom on which the neutron is bombarded and not exactly the nucleus .Isn't it ?

If you bombard an atom and miss the nucleus, do you think that fission will occur?

 

[Vibhor]

How the electrons associated with the parent nucleus are divided between the daughter nuclei is irrelevant to the fission process.

But the number of electrons divided is fixed/known depending on the type of daughter nuclei formed . Right ?

 

[jbriggs444]

But the number of electrons associated is fixed/known depending on the type of daughter nuclei formed .

A quick look into Wikipedia indicates that in a nuclear reactor, little or no ionization occurs. So that the original electrons are divided between the daughter nuclei according to their atomic numbers -- [or end up divided that way quickly enough so that it does not matter].

https://en.wikipedia.org/wiki/Nuclear_fission:

"However, in nuclear reactors, the fission fragment kinetic energy remains as low-temperature heat, which itself causes little or no ionization"

 

[Vibhor]

Thank you very much jbriggs .

 

[sophiecentaur]

A quick look into Wikipedia indicates that in a nuclear reactor, little or no ionization occurs.

If there were significant ionisation the wouldn't that imply the fissile material would not be a solid? Perhaps a local region of 'plasma' would be possible but they would recombine quickly.
Looking at the energies of gamma rays, we have 1Mev or more, where the energies of X rays, due to electronic transitions, are in the tens of kev region. I have a feeling that the timescale for the nuclear fission may be to short for the electrons to have time to change levels. Based on ideas of resonance (simple atomic theory) then interactions with high energies (nuclear) would perhaps not have high probability (??).