Problem

Predict the electron pair geometry and the molecu…

07:13

Problem 93 Easy Difficulty

What are the electron-pair geometry and the molecular structure of each of the following molecules or ions?
(a) $\mathrm{ClF}_{5}$
(b) $\mathrm{ClO}_{2}-$
(c) $\operatorname{TeCl}_{4}^{2-}$
(d) $\mathrm{PCl}_{3}$
(e) $\mathrm{SeF}_{4}$
(f) $\mathrm{PH}_{2}^{-}$

Answer

(a)
The central atom is chlorine which has seven valence shell electrons. The chlorine atom has five
fluorine atoms bonded to it and one lone pair of electrons. Since, it has five bond pairs and one
lone pair, electron pair geometry of $\mathrm{ClF}_{5}$ is octahedral and the molecular structure is square pyramidal.
see structure
(b)
In $\mathrm{ClO}_{2}^{-}$ , Chlorine is the central atom which has seven valence shell electrons and the negative
charge accounts for the presence of one extra electron. There are two oxygen atoms bonded to
it, hence there will be two bond pairs and three lone pairs for the compound. Hence its electron
pair geometry of $\mathrm{ClO}_{2}^{-}$ is tetrahedral and the molecular geometry is bent.
see structure
(c)
In $\mathrm{TeCl}_{4}^{2-}$ , tellurium is the central atom which has six valence electrons and the negative
charge accounts for two extra electrons. There are four chloride atoms are bonded to it, hence it
will have four bond pairs and two lone pairs. Thus its electron pair geometry of $\mathrm{TeCl}_{4}^{2-}$ is octahedral and the molecular geometry is square planar.
see structure
(d)
In $\mathrm{PCl}_{3}$ , Phosphorus is the central atom which has 5 valence shell electrons. There are three chloride atoms bonded to phosphorous atom, hence it has three bond pairs and one lone pair.
Thus its electron pair geometry of $\mathrm{PCl}_{3}$ is tetrahedral and the molecular geometry is trigonal pyramidal.
see structure
(e)
In $\mathrm{SeF}_{4},$ Selenium is the central atom which has six valence shell electrons. There are four chloride atoms attached to it, hence it has four bond pairs and one lone pair. Thus its electron
pair geometry of $\mathrm{SeF}_{4}$ is trigonal bipyramidal and the molecular geometry is seesaw.
see structure
(f)
In $\mathrm{PH}_{2}^{-}$ , Phosphorus is the central atom which has five valence shell electrons and the negative charge accounts for one extra electron. There are two hydrogen attached to it, hence it
has two bond pairs and two lone pairs. Thus its electron pair geometry of $\mathrm{PH}_{2}^{-}$ is tetrahedral and the molecular geometry is bent with $109^{\circ}$ bond angle.
see structure

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Chemistry 101

Chemistry

Chapter 7

Chemical Bonding and Molecular Geometry

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Video Transcript

Hi. This problem has several parts to it and were given several structures. And we want to know the electron pair geometry as well as the molecular structure. For this problem, I feel the best way to show this is to set up a little table. The first column. My table is gonna be valence electrons. That's gonna be the total number of electrons. When you add together the valence electrons for each element in the formula My next column I'm gonna go ahead and sketch out the DOT structure. The next column is going to be the electron pair geometry that refers to how Maney electron regions there are on that central Adam. How many pairs of electrons there are on that central atom, And then I'm going to finish off with the molecular structure. That's gonna be the shape of the actual molecule when you take into account the bonded atoms and the lone pairs. So let's get started. Letter A. We have CLF set F five rather adding the valence electrons together for five florins and one chlorine gives me 42 valence electrons. When I go ahead and do the structure for this, we have a chlorine surrounded by the four florins. And we put those electrons in. Okay, I'm sorry. There, five Florence. That's why I'm having a little trouble of my Matthew. Let me get that fifth flooring in there. Oh, yeah? Once I do that, that takes up 40 of the electrons. Gives me five bonds on the chlorine. But I still have another pair of electrons in other words, alone. Pair. Any time you have extra electrons, you put those on the central atom. So what we have are six distinct regions here. There are there are four Adams bonded. I'm sorry. Five atoms bonded and a lone pair. So we have five items bonded and alone pair, which is going to give us a total of six or an octahedron for the electron pair geometry because they're five atoms bonded. And that one lone pair for a total of six. When we look at the molecular structure, we only look at those five atoms bonded and look that lone pair as something that is pushing those away from each other. So that gives us a square pyramid. Okay, Alright, for let her be. We have Cielo two with a one negative charge that one negative charge means we need to add one extra electron after we add these up. So I'm going to add the seven electrons from chlorine and six plus six for the two oxygen's and then one more electron for that negative charge. And I see that we have 20 electrons to work with drawing out this structure. We put the loan element in the middle, but the two oxygen's on it. Okay on our little brackets to show that it has an extra electron in there. What we're seeing is we're seeing too. Pairs have bonded electrons and two lone pairs for a total of four. So two atoms bonded to lone pairs. A total of four. That means theorem. Tron, pair geometry. He's gonna be a tetra hydro. Since there are only two atoms bonded to that central Adam and two lone pairs, the actual molecular structure is going to be bent. All right, moving on, let her see. Let her see. We have t e c l four with a two negative charge. That means we're adding two extra electrons after we add a T E and and four cells, so we get a total of 36 sketching out this structure put the T in the center surrounded by the four C l's had in my electrons. For these four bonded atoms that takes up 32 of the 36 available available electrons. That means there are four more than I need to place on that central atom. In other words, this one here, this pair here and this pair here are gonna be lone pairs Gonna put brackets around this to remind the reader that it has two extra electrons. All right, so look what we have here. We have four bonded atoms and two lone pairs. That gives us a total of six electron regions. So that is going to be another Octa. He'd roll. However, only four of those six regions have atoms bonded to them, so the actual molecular structure is going to be a square plainer moving on toe. Let her d in letter d, we have PCL three. That gives us 26 electrons. Okay, r dot structure then is going to look like this. We have three atoms bonded on the central atom and we have one lone pair. So there is a total of three plus one or four electron regions. So this is again a tetra. He'd role in terms of the electron pair geometry. Yeah. Since there are three atoms bonded and one lone pair, the actual molecular shape ends up being trigeminal pyramidal. All right, let her e better e is S e f four. That would be 34 Valence electrons. We're gonna put the S E in the middle, surrounded by the four florins. Keep adding an octet of electrons around. Each of these takes up 32 of the 34 electrons. That means there's a pair remaining that is going to have to be expressed as a lone pair on the central atom. So on the central atom, there are four atoms bonded, and there's one lone pair for a total of five. So that means the electron para geometry gonna be trig onal by pyramidal. Okay to and this shape, since it's a 414 atoms bonded. One lone pair, the actual molecular structure. He's going to be that scientific term what we call seesaw, all right? And finally, I mean on two letter f f p h two, with the negative charge drawing this structure gives us a structure that looks like this with that extra electron he had. Therefore, there are two atoms bonded and there are two lone pairs on that central atom. So we're back again to a tetra. He'd roll. Since it's on, Lee has two atoms bonded to that central atom. It ends up bent. All right, so a quick review letter a has an electron pair geometry that gives it an actor. He drel. But it's actual molecular structure is a square pyramid. Let her be as a tetra. He Drel electron pair geometry. The actual molecular structure is bent. Let her see we're back to an Octa. He'd RL for the electron pair geometry. But this time the molecule shape this square plainer, I think for letter d molecular geometry Tetra he'd roll molecular shape. Since there are only three atoms bonded is gonna be trigeminal pyramidal. Let her e four atoms bonded. One lone pair on that central atom Trigano by Parham Perimeter All Yeah, molecular structure seesaw. And finally, letter f was a tetra. He'd roll for the molecular geometry or the electron pair geometry. Rather and the molecular structure ends up being bent. All right. Thank you so much. I hope you found this helpful

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