Which is the larger species in each pair? a. Li or Li⁺ b. Cs^- or Cs⁺ c. Cr^- or Cr³⁺ d. O or O^2-

Video transcript

Welcome back everyone to another video which is the larger species in each pair. A magnesium or magnesium two plus B iron negative or iron two plus C niobium negative or niobium five plus and D selenium or selenium two negative. There are four answer choices. ABC and D, they essentially correspond to a variation of those species. And now what we're going to do is solve this problem. Remembering a simple rule. If we have the same type of element, then the radius of the cion would be the smallest or by the radius of an atom or the radius of neutral species or by the radius of the anion. We can use this trend. And if we look at a, we're comparing exactly the same magnesium, just its neutral form and its cion. So we can say that the radius of magnesium is expected to be greater than the radius of magnesium two plus because neutral magnesium has a greater number of electrons relative to its c remember that its cion lost two electrons. And therefore it is smaller b the radius of iron negative is expected to be bigger than the radius of iron two plus once again, based on our trend. The first one is the anion which is expected to be the biggest. And the second one is the cion which is expected to be the smallest one. Now for C the radius of niobium negative just as in part B is expected to be greater than the radius of niobium five plus. Due to the same reason, we're comparing the anion of niobium versus is cion NLD the radius of selenium to negative will definitely be bigger than the radius of selenium because selenium to negative has an excess of two electrons relative to its neutral form and a greater number of electrons makes it bigger, right? We have greater repulsion forces and therefore neutral selenium would expand slightly to make this an ion. So now let's see what we have. If we're looking for larger species, we have magnesium iron, two negative niobium negative selenium two negative. And if we look at the answer choices, which would be the correct one. Well, essentially that's option. A option. A is the correct answer to this problem. Magnesium followed by iron, negative niobium negative and selenium two negative. Those are the larger species in each pair. Thank you for watching.