Write balanced nuclear equations for the following processes:

(b) selenium-72 undergoes electron capture.

Video transcript

All right. Hello everyone. So this question is asking us to provide the balanced nuclear equation for the electron capture process of iodine 120. Here we have four different entry choices labeled A through D proposing different possible equations. All right. So first, let's clarify a few things about isotope notation before we go ahead and draw out the reaction here, the equation. So let's say that I have a general element with an atomic symbol of X to the left of the atomic symbol are going to be two numbers one as a superscript on top and the other as a subscript on the bottom, the superscript on the top is going to represent the mass number that I'm going to abbreviate. Here is a, meanwhile, the subscript on the bottom here is the atomic number of that element abbreviated as Z. So A stands for the atomic mass and Z stands for the atomic number. So here our reactant is or one of our reactants I should say is iodine 120. So here iodine has the simple capital I and the superscript which is the mass number is going to be 120. Meanwhile, iodine has an atomic number of 53. So that should be the subscript. So now recall that during an electron capture process, iodine 120 as well as the electron that's being captured should be on the left side of the equation because both of these things are going to be the reactants here. So in addition to iodine 120 on the left side of the equation should be the electron. Now, the electron has a symbol of a lowercase E with a mass number of zero. And the subscript here should be negative one. So now our product is going to depend on what happens here. After electron capture, recall that on both sides of the equation, the values for the superscripts and the subscripts should balance out. So for example, if we're trying to find the atomic number of our daughter nucleus, which is our product, we'll call that A A should be equal to the sum of the superscripts on the left side of the equation. So 120 added to zero should equal A which represents the mass numbers or the mass number I should say of our product. So when balancing out the equation A is equal to 120. So now let's find the atomic number. Now, once again, the atomic number of the daughter nucleus should be equal to the sum of our subscripts on the left side of the equation. So 53 add it to negative one should equal Z which is the atomic number of the daughter nucleus. When balancing out this equation, we see that Z is equal to 52. And so our product has a mass of 120 an atomic number of 52. Now, the atomic number of 52 identifies our daughter nucleus as tellurium with a symbol of T. So, Tes are simple, 120 is the superscript, and 52 is the subscript and there you have it here is our balanced nuclear equation which matches option C in the multiple choice. And with that being said, thank you so very much for watching and I hope you found this helpful.