Compare and contrast the properties of ammonia and phosphine.

Video transcript

All right. Hi, everyone. So this question is asking us which of the following statements is true about the properties of ammonia and phosphate. And here we've got four different statements which we'll analyze as we go along in this video. Option A says one in two. Option B says two and three. Option C says 13 and four. Option D says two and four and option E says three and four. So let's go ahead and get started, right. Recall that the formula of ammonia, the molecular formula is NH three whereas that of phosphine is ph three. So let's go ahead and analyze statement one which says that ammonia is trigonal planar while phosphine is trigonal parameter. So let's start by finding the lowest structures of both compounds starting off with ammonia or NH three, right. So here we've got two different types of atoms being nitrogen and hydrogen. Now nitrogen, if you recall is in group five A, which means that it has five valence electrons. Now hydrogen has one valent electron, but we have three atoms of hydrogen in this compound which gives us a total of three valence electrons from hydrogen. And so when you added the total number of valence electrons from each atom, we get a total of eight valence electrons or R Lewis structure, which means that if I place nitrogen in the center and I create three bonds between nitrogen and each hydrogen, I'm going to have an extra loan pair of electrons on nitrogen. So now let's do the same thing for phosphine or ph three. Now recalled phosphorus is also in group five A with nitrogen, which means that it also has five valiant electrons. And so when we consider the number of valence electrons from our three hydrogens, that gives us three in total. Now, once again, when we add these two totals together, we get eight valence electrons, which means that phosphorus is going to be in the center of my Lewis structure. It's going to have three covalent bonds to each hydrogen or one to each hydrogen and phosphorus is going to have a lone pair of electrons as well. So if we consider the lowest structures of both ammonia and phosphine, both of them have three covalent bonds as well as one lone pair of electrons, which means that both of them are going to be trigonal parameter or they're both going to have trigonal para meal geometry. So here statement one is going to be incorrect, right? Because both ammonia and phosphine are trigonal parameters. So now lets consider statement too. Statement two says that ammonia is a good proton acceptor while phosphine is not. Now recall that the term proton acceptor refers to the compound's ability to behave as a base. Right now recall that ammonia is a good proton acceptor because it is a good base. While phosphine is not because ammonia can react with water to form aqueous basic solutions, where is FF does not exhibit that property and aqueous solutions of phosphine remain neutral. Right? So statement two is correct because ammonia is a good proton acceptor while phosphine is not. Next up here is statement three, which says that ammonia cannot exhibit hydrogen bonds while phosphine can't. No recall that hydrogen bonding or h bonding is only possible when you have hydrogen connecting to an electron atom or en for short as I'm writing on the screen here. Now, when we refer to a highly electron atom, we're referring specifically to nitrogen, oxygen and fluorine. So because ammonia does in fact contain nitrogen, it's therefore the one that can exhibit h bonding whereas phosphine cannot, right. So statement three is incorrect because ammonia does exhibit h bonding whereas phosphine cannot. And then uh statement four says that at room temperature, both ammonia and phosphine are colorless gasses and recall that this is true, right? Both ammonia and phosphine are in fact colorless gasses at room temperature. So of the four statements given only two and four are correct, which means that our answer is going to be option d in the multiple choice. So with that being said thank you so very much for watching. And I hope you found this helpful.