Is charge conserved in positron emission?

[Bipolarity]

Consider the reaction:

$^{39}_{20}Ca \rightarrow ^{39}_{19}K + \beta^{+}$

I understand that a proton in the Calcium nucleus is being split into a neutron, which stays in the nucleus, and a positron, which gets ejected.

But if you look at the equation above, charge is not conserved. The only thing I can think of doing to balance is to consider the potassium product as a negative ion, but that makes no sense to me?

Or perhaps I am missing something. Or perhaps it has something to do with the number of electrons in play.

Any help is appreciated. Thanks!

BiP

 

[Borek]

Charge is conserved always. Equation is just not complete, but when writing nuclear reaction we don't pay much attention to such things, we concentrate on what is important from the point of view of the nucleus (this is not a chemical reaction). Once the positron is emitted you end with an excess electron in the atom shells. Later this electron will look for a better place for itself, which usually means traveling to some other atom/ion whatever.

 

[Bipolarity]

I see! Thanks Borek!
So techniclly, the potassium is actually an anion but we don't really care about that charge in nuclear reactions since the electron will quickly move somewhere else right?

BiP

 

[Borek]

More or less.

Depending on the nuclear reaction it may happen that nucleus (or several) lands in a different place it originally was (think fission). They move independently from the electrons generating a mess on their way (there is a reason why we call some forms of radiation ionizing).

 

[LudusRex]

Your understanding of the reaction is correct. Charge is not conserved in this reaction, as the total charge on the reactant side (20) is not equal to the total charge on the product side (19 + 1).

However, it is important to note that charge conservation is a fundamental law in physics and is always observed in all processes. In this reaction, the missing charge is accounted for by the conversion of a proton into a neutron. Neutrons have no charge, so the total charge is still conserved.

Additionally, the positron that is ejected has a positive charge (+1), balancing out the negative charge of the electron that is left behind in the nucleus. This maintains overall charge neutrality in the reaction.

In terms of the potassium product being considered a negative ion, that interpretation does not make sense in this context. The potassium atom is still neutral, with the same number of protons and electrons.

Overall, while it may seem like charge is not conserved in this reaction, it is actually accounted for through the conversion of a proton into a neutron and the balancing of positive and negative charges.