The two most common isotopes of uranium are 235U and 238U. (d) 238U undergoes radioactive decay to 234Th. How many protons, electrons, and neutrons are gained or lost by the 238U atom during this process?

Video transcript

welcome back everyone in this example, we need to determine which of the following statements is true. When plutonium 2 44 undergoes radioactive decay to uranium 2 40. So according to our prompt, we know that we are beginning with our plutonium 2 44 Which apparently decays to uranium 2 40. So we want to recall our atomic number first for plutonium which from the periodic table is a value of 94. Recall the atomic number is written here, so we can say Z is equal to 94 because recall the atomic number is represented by the symbol Z for uranium, Z is equal to 92. We recall now we also want to recall that our atomic number is equal to our number of protons, which we would recall is also equal to our number of electrons for neutral atoms only. And so because we understand that our proton should equal our number of electrons in neutral atoms only. And according to the prompt were given plutonium and uranium with no ionic charge, meaning that these are neutral atoms. We would assume that we therefore have 94 protons for plutonium and 92 protons for uranium, meaning we would have 94 electrons as well in plutonium and 92 electrons in uranium. And because we know that we went from having 94 electrons to 92 electrons in our formation of uranium 2 40. That means that we would have a loss of two electrons. So we have 94 electrons Because we have 94 protons here, we have 92 electrons because we have 92 protons. So we have a loss of two electrons since we formed our uranium 2 40. And what this means is that we likely went through the type of radioactive decay specifically being a alpha particle decay. So we would have, we recall that an alpha particle has a mass number of four and has an atomic number of two and it corresponds to the atom helium. So this is therefore an alpha or we can just say alpha decay of our plutonium 2 44. Now looking at the statements given, were given the number of protons electrons as well as neutrons. So we need to determine how many neutrons Plutonium 2 44 has. And we would recall that our name of our isotope of plutonium which has our mass number here. So recall that this is our mass number. This should be able to help us figure out our number of neutrons because we would recall that our mass number is our protons added to our neutrons. And so because we know that for plutonium 2 44 we have a mass number of 2 44. We're going to subtract that from our number of protons, which above we stated is 94 protons, so minus 94 protons. This is going to give us a difference equal to a value of 150. So we have 150 neutrons in our plutonium 2 44. And we want to figure out how many new neutrons we have in in uranium 2 40. So Given in our mass number, we have the mass number 2:40 subtracted from our number of protons, which above we stated is 92 protons from the atomic number of uranium. And this difference gives us a total of 148 neutrons. And so to find the difference in neutrons, we would take 1 50 minus 1 48 and that's going to give us a difference of two neutrons in our alpha decay. And so we can confirm that we determined that we are undergoing a loss of two electrons because we have an alpha decay here which also corresponded to A difference of two neutrons lost from our plutonium as well as a loss of two protons. Since we lost us two electrons. Because we ended up with the atomic number and sorry about that, we ended up with the atomic number being 92 for uranium. And so that means that the only correct answer choice we can confirm would be choice b. So I hope that everything are viewed was clear. If you have any questions, leave them down below. And I will see everyone in the next practice video