Draw three-dimensional structures of PCl3 and PCl5, and
then explain why one of the molecules has a dipole moment
and one does not.

Question

Draw three-dimensional structures of PCl3 and PCl5, and 
then explain why one of the molecules has a dipole moment 
and one does not.

Accepted Answer

Hello everyone today. We have the following problem provide the structure of the molecules for arsenic. Try fluoride and arsenic. Penta fluoride showing their spatial orientation identify. Which has a dipole moment in which does not and explain your answer. Well, first we have to determine what it means to have a spatial orientation. So in chemical formulas and chemical structures you tend to have three major parts of it. You either have a line, you have a dash or you have a wedge. So a line is essentially going to be within the same plane. So within the same plane a dash is going to represent something that is towards you. And that leaves a wedge which means it's going to represent things or structures that are away from you. And so now we can focus on our structures. So first we have arsenic try fluoride. We have arsenic Being a group five A element And therefore having five valence electrons. And then we have a floor in here which is a group seven a electron and therefore has seven valence electrons. However, there are three of them. So that gives us 21 total for flooring. And then in total We have electrons to construct our figure. And so we know that we're going to have arsenic surrounded by three florins If 1, 2 and three. And now we have to distribute these electrons. So we're going to get flooring six electrons around each one to complete our octet rule and then we have two electrons left over. And then we're going to give those two are arsenic there noting our dipole moments Florina is more electro negative than arsenic due to its position on the periodic table. So we're going to draw a dipole moments going towards each flooring and this essentially produces a net die pole in the downwards direction. So we have a net dipole moment and the downwards direction. Next we're going to know its geometry and the geometry of this is actually going to be tribunal pyramidal. And so we can also note that our di pole moments. So our dyp holes don't cancel out. So that indicates this is going to be a polar molecule. Next we move on to our arsenic pencil fluoride using the same procedures as we did before, We say that arsenic is going to have five valence electrons. And then flooring is going to have seven valence electrons. However, there are five in this situation here giving us 35 there. And in total we have 40 electrons for our figure. We know we have one arsenic and this time it's going to be surrounded by five different florins. 34 and five as before, flooring is going to get six electrons around each one to compensate for the octet rule and we don't have any more for arsenic. Now we draw dipole moments and we said before that flooring is more electoral negative. So we draw our di pole moments towards flooring. And we can see here that there is no that's dyp hole because none of the arrows are pointing towards where the arrows in general are not pointing toward the general direction. So next we're going to move on and say that the geometry is triggered by pure middle. However, in this case our die poles cancel out, so it is going to be non polar. So essentially the structure that has a dipole moment is going to be arsenic try fluoride and the structure that has no dipole moment, it's going to be arsenic, Penta fluoride. And with that we've answered the question overall, I hope this helped and until next time.

Draw three-dimensional structures of PCl3 and PCl5, and then explain why one of the molecules has a dipole moment and one does not.

Verified Solution

Key Concepts

Molecular Geometry

Polarity and Dipole Moment

Valence Shell Electron Pair Repulsion (VSEPR) Theory