Order the following ions from smallest to largest: Sr2+, Se2-, Br...

Question

Order the following ions from smallest to largest: Sr2+, Se2-, Br-, Rb+.

Accepted Answer

Hey everyone in this example, we need to identify the elements or ion that is larger in size for each of the given sets. Before we do so, we want to recall our facts on atomic size corresponding to our ionic charge and our total electrons. So what we want to recall is that the greater the amount of electrons in an atom will correspond to a larger atomic radius for atom. The second thing we want to recall is that the more positive our ion that's going to relate to a loss of electrons in the atom and the more negative our ion will relate to our atom gaining electrons. And lastly, we want to go ahead and recall that when we have so electronic atoms or ions, we're going to be recalling that this means that they have the same number of electrons, whether they're an ion or an atom, a neutral atom. And so we're going to be determining which is greater in size by referring to the electronic charge on the ion. And so the more negative the charge, for example, something with a negative three charge that will correspond to increasing size. So a -3 ion is going to be greater in size by its atomic radius compared to a ion with a minus two charge, then compared to an ion with a minus one charge and then so on and so forth as we go down the spectrum All the way to positive three. And when we get to positive three, for example, we would go ahead and say that we are decreasing significantly in our atomic size. So now that we have this laid out, let's go ahead and determine our answers. So for part A we're comparing the sulfur atom to a sulfide an ion Again, we want to recognize that our sulfide an ion is more negative. It has a 2 - charge, meaning it has two extra electrons compared to the neutral atom of Sulfur. And so we would say that because this is more negative, it therefore has more electrons. And so therefore our sulfide an ions radius is going to be larger than our sulfur atoms radius. So we would go ahead and box in as our answer. The sulfide an ion because it's larger in size. Moving onto choice B. We have the nitride an ion versus the nitride cat ion. Now in this case we're gonna want to go ahead and recall again that the more negative our charge that is associated with a gain of electrons. And so the more electrons we have attached to our atom, we have a greater atomic radius meaning a larger atoms size. And so in this case we have a negative charge on our nitride an ion. So we would say that the an ion is negative and has an extra electron. And so therefore our night rides radius is going to be greater than the nitride cat ion radius which is missing an electron because it has that plus charge. So we would go ahead and box in the night. Tried an ion. Moving onto choice see we're comparing a neutral barium atom to a caddy on B A. Two plus again, we recognize that the neutral barium atom is not missing two electrons like the barium kati on here because we recall that the positive charge means that it's missing two electrons. And so the barium cat ion has more electrons. And so therefore sorry, the barium neutral atom has more electrons. So we would box that one in because we would say that therefore barium radius is going to be greater than that of the barium cat ions radius which is missing electrons. Two electrons specifically. And lastly we have the copper an ion compared to our copper cat ion. And so again we're missing two electrons on our copper cat ion whereas our copper and ion has an extra electron and so we have more electrons on our copper and ion and so are copper and ions radius is going to be greater than that of our copper cat ions radius. So we would go ahead and box in our copper an ion as our final choice to complete this example as our answer for the largest or the larger atomic radius in the set. So if you have any questions, please leave them down below. Otherwise, I will see everyone in the next practice video

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