(b) Describe what is meant by a three-center, two-electron bond.

Video transcript

All right. Hi, everyone. So for this question, let's identify whether the following statement is true or false. Every bond in di A la A L two H six is a three center two electron bond. Now recall that the ordinary covalent bond is described as a two center two electron bond or two C two E. And the reason for this is because the ordinary covalent bond is composed of two electrons being shared in between two atoms. However, some molecules can have what are known as three center two electron bonds in which two electrons are being shared by three atoms instead. So first, we have to figure out the structure of a two H six and we do that by first calculating how many valent electrons we have in torque. Right. In this case, we have two different types of atoms. We have aluminum and hydrogen aluminum is in group three A which means that it has the three valence electrons, no three valent electrons multiplied by the two atoms of aluminum that we have in dy ala gives us a total of six electrons. Thus far. Now hydrogen has one valent electron which when multiplied by the total number of hydrogen atoms which is six, gives me a total of six electrons as well. And when I add these two quantities together, I get that there are a total of 12 valence electrons in this compound. Now, assuming all of the bonds in al two H six have to be too center to electron. That means that if I divide my number of valent electrons by two, that should give me a total of six bonds in the structure of di ale. However, right, the structure of Diala is as follows, right, each atom of aluminum has two bonds to a hydrogen. However, two hydrogen atoms must be in between or two aluminum atoms. So what that means right is that there are actually eight bonds in the structure of diala despite having 12 valence electrons only. Now, the dashed lines in the center represent bonds that are the re center to electron. And because we have two of these, there are a total of four electrons coming from our three center, two electron bonds. So of the 12 valence electrons that we have, right, four of them are from are three center to electron bonds, which means that we have a total of eight electrons that are still unaccounted for until we consider the fact that each aluminum is bound to two hydrogens as well. So that means that I have a total of four bonds remaining, which means that each one of them contains two electrons per bond. So even though I have three center, two electron bonds in my structure of die Allen, I do have two center, two electron bonds as well, which means that not every bond in Da Allen is three center two electron. Therefore, right, the statement given in the text of the question is false and there you have it. So with that being said, thank you so very much for watching and I hope you found this helpful.