Use VSEPR theory to answer the following questions: (a) Which molecule, BF3 or PF3, has the smaller F¬X¬F angles?

Video transcript

Hey everyone, we're asked based on the vesper theory determine whether xenon tetrachloride or carbon tetrachloride will have smaller chlorine, X chlorine angles with X being either xenon or carbon. So first let's go ahead and draw out our lewis structure for xenon tetra chloride. We want to determine the total number of electrons will have in our structure. So starting with xenon, we know that this is in our group A. So we have eight valence electrons. And since we have one of xenon we're going to multiply that by one. In order to get eight electrons. Now looking at Chlorine, we know that chlorine is in our group seven a. So we have seven valence electrons from chlorine and we're going to multiply that by four. Since we have four of chlorine, this will get us to a total of 28 electrons. Now when we add these two values up we get a total of 36 electrons. So when we draw this out we know that xenon is going to be our central atom since it is less electro negative. And now when we add our chlorine we're going to add four chlorine, filling up our chlorine docked, it's We find that we still need to add two lone pairs. So we're going to add those lone pairs on to our xenon and this is okay because xenon can disobey the octet rule looking at our lewis structure, we can see that we have six electron groups. Since we have four atoms and two lone pairs and this means that this will be Octa hydroxyl and as we've learned Octa he'd roll has A degree of 90° and 180°. And since we're looking specifically at our chlorine, xenon chlorine angle, This is going to be 90°. Now let's go ahead and draw out our carbon tetra chloride. Again, we want to take the same steps. We know that carbon is in our group for a and it will have four valence electrons since we only have one of carbon, we're going to get a total of four. Next looking at our chlorine, we know that this is in our group 78 and we're going to multiply this by four since we have four of chlorine, this will get us to 28. Now, when we add these two values up, we get a total of 32 electrons. Now let's go ahead and draw out our lowest structure. We know that carbon is going to be our central atom since it is less electro negative and we're going to add our four chlorine. And when we fill up our octaves for our chlorine, We find that we end up with 32 valence electrons. So this is going to be the final louis structure for carbon tetrachloride. Now, looking at our electron groups, we can see that we have four electron groups since we have four atoms and zero loan pairs. So this means that we have a tetra federal shape. And as we've learned, this will be 109.5° which is also going to be the degree between our chlorine carbon chlorine angles. Now, when we compare the two angles, we can see that 90 degrees is less than 109.5 degrees. So that means xenon tetrachloride will have smaller chlorine, x chlorine angles, which is going to be our final answer. Now, I hope that made sense and let us know if you have any questions.