Question

Question #233da

Answer 1

What we need is one electron.

Explanation:

The top numbers represent mass numbers, the total of protons plus neutrons. This quantity must be conserved, although protons can interchange with neutrons. To get the same total of `241` on both sides of the equation, then we find that something has to have a mass number of zero. Or maybe thete is nothing at all, but ... there is one more thing to check, which we will get to. For now, render this:

`239+(2×1)=241+color(blue)(0)`

`" "_(94) ^(239) "Pu" + 2 " " _0 ^1n\rightarrow " "_(95) ^(241) "Am" + color(blue)(" " _? ^0?)`

Now for the lower numbers. This represents the total charge in electron or proton units, a positive number means a positive charge and a negative number means a negative charge. Note that for an atomic nucleus where all the positive charge is protons, this is the atomic number of the element. Then since charge has to be conserved the products have to have `94` net positive charges like the reactants:

`94+(2×0)=95+color(red)((-1))`

`" "_(94) ^(239) "Pu" + 2 " " _0 ^1n\rightarrow " "_(95) ^(241) "Am" + color(red)(" " _(-1) ^0?)`

Now we see what we need to add: something with one negative charge but carrying no protons or neutrons (no heavy particles at all). That would be one electron:

`" "_(94) ^(239) "Pu" + 2 " " _0 ^1n\rightarrow " "_(95) ^(241) "Am" + color(purple)(" " _(-1) ^0e)`

Note that the electron is not part of any atom in this reaction. We have only the plutonium nucleus and a couple neutrons to start with. The electron came from an unstable intermediate product that quickly decayed by beta particle emission, and the beta particle is the electron. The americium product also decays slowly, but it has a long enough half life for practical uses such as smoke detectors.