Which of the following pairs of elements would you expect to have...

Question

Which of the following pairs of elements would you expect to have the most similar atomic radii? 
a. Si and Ga 
b. Si and Ge 
c. Si and As

Accepted Answer

Hey everyone in this example, we need to identify which pair is closest in size of atomic radius. So we want to go ahead and recall our trend for atomic radius on our periodic tables. And we should recall that as we go from the left to the bottom right of our periodic table, atomic radius is going to be decreasing. So beginning with example one we recognize that we're given oxygen and chlorine. We would find oxygen across Period two on our periodic table in group six A. And compared to chlorine which were given in our pair, we would find chlorine across Period three on our periodic table In Group seven A. So what relates this pair most to one another is how close their group number is from one another. We have our oxygen and group six A. Which is only one unit away from Group seven A. On our periodic tables. And so because we also recognize that chlorine is in the energy level three in period three of our periodic tables, we only have the difference of one energy level that is affecting the atomic radiance is between these two atoms. So we're going to go ahead and say that before we can confirm our answer choice, we want to analyze the other two answer choices first. So moving on to the next pair, we have oxygen versus phosphorus. We recall that the location for phosphorus on our periodic table is that it's located in group five a. Across period three. Next we want to go ahead and consider our third pair given Where we have oxygen being compared to sulfur on our periodic tables where sulfur we recall is in group six a. Across Period three as well. Now, as you can see based on our locations of each of the given atoms, we would recognize that each of these atoms are in the third energy level on our periodic tables and therefore would have a larger atomic radius all compared to the oxygen atom in their pair. However, we want to find which of these three atoms here between chlorine, phosphorus and sulfur would have the smallest radius, which would then therefore be closest in size to oxygen as a pair. And so the smallest radius again based on our trend, is going to correspond to the group number that is left most on our periodic table. Or sorry to the right most of our periodic table. Because we said that atomic radius decreases as we go from the left to the bottom right of our periodic table. And so based on our group numbers, we would see that group seven a. Which falls right over here on our periodic tables is the most to the right based on our atomic radius trend. And so because it's in group seven, a we would say therefore it has the smallest radius between our atoms, phosphorus, sulfur and then also oxygen. And so to complete this example, we would confirm that the first pair, oxygen and chlorine are therefore closest in size of atomic radius. So I hope that everything be viewed was clear. If you have any questions, please leave them down below, and I will see everyone in the next practice video.

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