When can an atom expand its octet in bonding?

[Lazerous]

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For question 163 in GChem destroyer. How was I supposed to know that Cl could expand its octet like that? If you don't have destroyer then the molecule in question is ClF5

 

[topdent1]

I also want to know the answer. All I know is that certain atoms in the 3rd and 4th period can expand their octet due to the d-shell. I think Cl, S, Xe, and maybe some others.

 

[PooyaH]

Just count the valance electrons guys. You have a total of 42 valence elctrons and Cl makes 5 bonds with 5 Fs...that's (8x5) 40 electrons. So there must be still 2 electrons left!!!

 

[Lazerous]

Just count the valance electrons guys. You have a total of 42 valence elctrons and Cl makes 5 bonds with 5 Fs...that's (8x5) 40 electrons. So there must be still 2 electrons left!!!

I was always under the impression that unless they have d-orbitals then an atom can have no more than 4 things bonded to it, but I guess that is not true.

OK, another question. Destroyer GChem #166...I understand why removal of the product in an irreversible rxn does not affect the rate.

BUT what if it was a reversible rxn, would it change the rate of the reaction even though reaction rate only depends on the concentration of the reactants? If yes, then is it due to LeChat's principle?

 

[td4azklz]

Just count the valance electrons guys. You have a total of 42 valence elctrons and Cl makes 5 bonds with 5 Fs...that's (8x5) 40 electrons. So there must be still 2 electrons left!!!

I'm sorry, I dont have destroyer yet so I can't look at the problem, but where are you getting your 8 from?

 

[doc3232]

Cl made 5 bonds?? I don't think that is possible.
Please explain it.

 

[PooyaH]

I'm sorry, I dont have destroyer yet so I can't look at the problem, but where are you getting your 8 from?

For an atom to be octat it needs to have 8 valence electrons right?

 

[td4azklz]

For an atom to be octat it needs to have 8 valence electrons right?

i should've known that.

 

[PooyaH]

i should've known that.

So with problems like this, first count the valance electrons of each atom, then make sure at the end you get the same number of electrons.

 

[Lazerous]

Cl made 5 bonds?? I don't think that is possible.
Please explain it.

That's what I was thinking at first. If I had this question on the actual DAT and "None of the above" was an aswer choice I would have selected.

I'm still not entirely sure how it is possible for it to bond to 5 other atoms. I only thought atoms like S or P could expand their octet to beyond 4 bonds.

 

[td4azklz]

How do you get 42 valence electrons? I'm kind of not following...

 

[Lazerous]

How do you get 42 valence electrons? I'm kind of not following...

OK, so we have 5 Fluorine's and 1 Chlorine. You can determine the number of valence electrons by either doing the hybridization or simply looking at the group # the atoms are contained in. Both F and Cl are in group 7. So they both have 7 valence electrons.

Since we have 5 F's you do: 5*7= 35
Since we have only 1 Cl do: 1*7= 7

Add both up and you get 42 electrons. One bond has 2 electrons, and we have 5 bonds so that is 10 electrons that got used up. the rest of the 32 you distribute as lone electron pairs around the F first and then whatever is left you give it to the central atom. Which in this case is Chlorine.

 

[pbure9]

Cl made 5 bonds?? I don't think that is possible.
Please explain it.

Cl is 3s^2 3p^5 so it can hybridize to make a sp3d orbital, which it does in ClF5.

So in this case you have Cl being capable of making 5 bonds (from sp3d), with the other two electrons being lone pairs on Cl.

 

[pbure9]

That's what I was thinking at first. If I had this question on the actual DAT and "None of the above" was an aswer choice I would have selected.

I'm still not entirely sure how it is possible for it to bond to 5 other atoms. I only thought atoms like S or P could expand their octet to beyond 4 bonds.

Other atoms like Te can make 6 bonds.

Xe is 5s^2 5p^4. It can hybridize to sp3d2 giving it potential to be 6 bonds (ex. TeF6).

 

[td4azklz]

Other atoms like Te can make 6 bonds.

Xe is 5s^2 5p^4. It can hybridize to sp3d2 giving it potential to be 6 bonds (ex. TeF6).

Isnt Xe 5s^2 5p^6?

 

[doc3232]

Cl is 3s^2 3p^5 so it can hybridize to make a sp3d orbital, which it does in ClF5.

So in this case you have Cl being capable of making 5 bonds (from sp3d), with the other two electrons being lone pairs on Cl.

Ok, a genchem concept I completely don't understand, but what you said sparked some memories...please continue explaining... how did it become sp3d?
Thanks

 

[td4azklz]

Ok, a genchem concept I completely don't understand, but what you said sparked some memories...please continue explaining... how did it become sp3d?
Thanks

Yeah, i'd like to know as well

 

[pbure9]

Isnt Xe 5s^2 5p^6?

sorry, thats correct i meant to say Te is 5s2 5p4.

 

[pbure9]

Ok, a genchem concept I completely don't understand, but what you said sparked some memories...please continue explaining... how did it become sp3d?
Thanks

we we can look at a simpler version of hybridization in carbon. carbon has 4 electrons. Looking at valence electrons it has two electrons in 2s and two in 2p. Electrons are first sorted into the 2s and then into the 2p, but if you remember they go in 1 by 1 into each "slot" _ _ _ the once you get to the end the electrons pack with oppsoite spin from the beginning (i cant explain this that well w/o using a picture but i hope you guys remember this). So here you have two electrons that can make a bond (from the two lone electrons in 2p orbital), but how does carbon make 4 bonds in CH4. It redistributes its electrons from the 2s orbital and hybridizes into the sp3 orbital _ _ _ _. It now has 4 lone electrons that can acceot 4 other electrons aka 4 bonds!

Hope that helps let me know...i could do a better job if i could draw it out though =/

 

[Lazerous]

Cl is 3s^2 3p^5 .

OK, so simply based off of this information how were you able to ocnclude that Cl can be sp3d hybridized?

 

[appleonius]

OK, so simply based off of this information how were you able to ocnclude that Cl can be sp3d hybridized?

bah...disregard.

 

[pbure9]

OK, so simply based off of this information how were you able to ocnclude that Cl can be sp3d hybridized?

well i dont think you really have to know that for this question. However, based on it, ClF5, Cl has enough electrons to hybridize into an sp3d orbital, and it will even have 2 left over, which is why it has a lone pair on it.

I dont think it has to be looked at as a hybridization question, just as it was discussed earlier, count up the valence electrons and you'll get your answer, but it just helps knowing that Cl can make 5 bonds because of hybrization.

 

[Lazerous]

well i dont think you really have to know that for this question. However, based on it, ClF5, Cl has enough electrons to hybridize into an sp3d orbital, and it will even have 2 left over, which is why it has a lone pair on it.

I dont think it has to be looked at as a hybridization question, just as it was discussed earlier, count up the valence electrons and you'll get your answer, but it just helps knowing that Cl can make 5 bonds because of hybrization.

Sorry for all the questions.

So since in the original question (ClF5) Cl has 2 electrons left over; does that mean it can form two more bonds and possible be ClF7 ???

 

[pbure9]

Sorry for all the questions.

So since in the original question (ClF5) Cl has 2 electrons left over; does that mean it can form two more bonds and possible be ClF7 ???

probably not. from what i know from genchem, i've never seen a molecule hybridize past 6 domains, which would be an octohedral. There is such a thing as [ClF6]- though.

Te or Xe, for example can make 6 bonds with F (thats sp3d2 hybridization)

 

[Lazerous]

probably not. from what i know from genchem, i've never seen a molecule hybridize past 6 domains, which would be an octohedral. There is such a thing as [ClF6]- though.

Te or Xe, for example can make 6 bonds with F (thats sp3d2 hybridization)

OK, I finally got it now. Thanks!
So no more than 6 bonds on any atom (as far as this exam is concerned at least) and Cl can have up to 6 bonds but it would have an overall negative formal charge. Got it.