# Lewis structure help :(

Watch
Announcements
#1
Hey so im having trouble drawing lewis structures. So with the example XeOF4:

I assume Xe is the central atom as it is the least electronegative then i attach the other atoms with single bonds. But how do i know if i should put the remaining electron pairs as double bonds or lone pairs?

Thanks
0
2 years ago
#2
Have you not learnt how atoms bond to each other covalently and the way they share electrons? apply those basic rules here and it should work.

Important thing to look for is the number of valence electrons and then go on from there.
0
#3
Have you not learnt how atoms bond to each other covalently and the way they share electrons? apply those basic rules here and it should work.

Important thing to look for is the number of valence electrons and then go on from there.
Yes i have but im not sure how to apply this to drawing lewis structures

So ive added all the valence electrons. I had to draw one extra for oxygen and one less for Xe so it would fit but obviously this is wrong. Where do i go from here?

0
2 years ago
#4
(Original post by kiiten)
Yes i have but im not sure how to apply this to drawing lewis structures

So ive added all the valence electrons. I had to draw one extra for oxygen and one less for Xe so it would fit but obviously this is wrong. Where do i go from here?

You are missing out an important fact. How many electrons does each atom contribute? Take a look and you will realise something.
0
#5
You are missing out an important fact. How many electrons does each atom contribute? Take a look and you will realise something.
At the moment they are all contributing one electron???
0
2 years ago
#6
(Original post by kiiten)
At the moment they are all contributing one electron???
Nope. Look at how many electrons Xe, F and O have in their outer energy level. Then see how they each contribute electrons.
0
#7
Nope. Look at how many electrons Xe, F and O have in their outer energy level. Then see how they each contribute electrons.
Oh yeah oops

Xe - 8 outer electrons (contributes 5)
F - 7 outer electrons (contributing 1)
O - 6 outer electrons (contributing none???)
0
2 years ago
#8
(Original post by kiiten)
Oh yeah oops

Xe - 8 outer electrons (contributes 5)
Fe - 7 outer electrons (contributing 1)
O - 6 outer electrons (contributing none???)
Fe? It's Fluorine so should be F? Also, when bonding, how many lone pairs does O have generally which it can contribute? F can contribute how many electrons to have a complete orbital? What do you think?
0
#9
Fe? It's Fluorine so should be F? Also, when bonding, how many lone pairs does O have generally which it can contribute? F can contribute how many electrons to have a complete orbital? What do you think?
yeah sorry its F, idk whats wrong with me today

F needs 1 more electron for an octet and oxygen needs 2??
0
2 years ago
#10
(Original post by kiiten)
yeah sorry its F, idk whats wrong with me today

F needs 1 more electron for an octet and oxygen needs 2??
Okay. So there are a total of 42 valence electrons. 8 from Xe, 6 from O and 28 from F (7 from each F atom). You know that Xe will be the central atom. now figure out how it will bond with Oxygen so it has a full energy level. After you figure this out, Fluorine should be relatively simple.
0
#11
Okay. So there are a total of 42 valence electrons. 8 from Xe, 6 from O and 28 from F (7 from each F atom). You know that Xe will be the central atom. now figure out how it will bond with Oxygen so it has a full energy level. After you figure this out, Fluorine should be relatively simple.
Ok so i know its a double bond but how do you decide this? Is it because oxygen needs 2 electrons to form an octet?
0
2 years ago
#12
(Original post by kiiten)
Ok so i know its a double bond but how do you decide this? Is it because oxygen needs 2 electrons to form an octet?
Yes. Oxygen and Xe will have a double bond because that is the way Oxygen will achieve a double bond. Now, decide how other atoms will pair
0
#13
Yes. Oxygen and Xe will have a double bond because that is the way Oxygen will achieve a double bond. Now, decide how other atoms will pair
Oh so its based on the number of electrons needed to achieve an octet?

So fluorine needs 1 electron - single bond
Oxygen needs 2 - double bond
Xenon - .... already has an octet?? Im confused
0
2 years ago
#14
(Original post by kiiten)
Oh so its based on the number of electrons needed to achieve an octet?

So fluorine needs 1 electron - single bond
Oxygen needs 2 - double bond
Xenon - .... already has an octet?? Im confused
you are right that fluorine needs 1 electron to have a full octet but there are 4 F atoms so you will have 4 single bonds. Therefore, in total you have

one double bond + 4 single bonds = 4 + 8 electrons which means 12 valence electrons have been used and you are left with 30 valence electrons.
0
#15
you are right that fluorine needs 1 electron to have a full octet but there are 4 F atoms so you will have 4 single bonds. Therefore, in total you have

one double bond + 4 single bonds = 4 + 8 electrons which means 12 valence electrons have been used and you are left with 30 valence electrons.
so 15 electron pairs? - add as valence electrons??

generally speaking for lewis structures do you draw the single bonds then add valence electrons. Then how do you decide if you need a multiple bond i.e. double/triple etc.??
0
2 years ago
#16
(Original post by kiiten)
so 15 electron pairs? - add as valence electrons??

generally speaking for lewis structures do you draw the single bonds then add valence electrons. Then how do you decide if you need a multiple bond i.e. double/triple etc.??
Yes there are 15 electron pairs and you add them as lone pairs to each atom in your structure.

I personally don't see a big difference with questions of this type. You know O will have a double bond even if you don't work out the valence electrons. Although generally it is better to work out the valence electrons and then see what bonds are formed but saying that, doing it either way is fine because it doesn't make a big difference.
1
#17
Yes there are 15 electron pairs and you add them as lone pairs to each atom in your structure.

I personally don't see a big difference with questions of this type. You know O will have a double bond even if you don't work out the valence electrons. Although generally it is better to work out the valence electrons and then see what bonds are formed but saying that, doing it either way is fine because it doesn't make a big difference.

Would you be able to help me with this too??
https://www.thestudentroom.co.uk/sho....php?t=5087614
0
2 years ago
#18
(Original post by kiiten)

Would you be able to help me with this too??
https://www.thestudentroom.co.uk/sho....php?t=5087614
Np. Unfortunately, my knowledge ends here Although there are several other users who can help you
0
2 years ago
#19
(Original post by kiiten)

Would you be able to help me with this too??
https://www.thestudentroom.co.uk/sho....php?t=5087614
If you're an undergraduate it is also worth working out the shape that the compound will adopt based on VSEPR theory.

You have already established that you have 5 atoms bonded to Xe (note, although the double bond to O is obviously a 4 electron bond, for the purposes of VSEPR it counts as one group, the same as a single bond.

You have also worked out there are 15 electron pairs that are not bonding.
You should know that double bonded oxygen will have 2 lone pairs and that single bonded Fluorine will have 3 lone pairs.

so that's 4x3 for the Fluorines and 2 for Oxygen
that accounts for 14 lone pairs

So the 15th lone pair must be on the Xenon!

From that you can conclude that there are 5 bonding groups and one lone pair around Xe, so the geometry around Xenon should be square pyramidal (which indeed it is)!
0
#20
(Original post by MexicanKeith)
note, although the double bond to O is obviously a 4 electron bond, for the purposes of VSEPR it counts as one group, the same as a single bond.
Wait im confused. A double bond counts as 4 electrons which means xenon already has 8 electrons so why does it have a lone pair?
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### Should there be a new university admissions system that ditches predicted grades?

No, I think predicted grades should still be used to make offers (579)
34.32%
Yes, I like the idea of applying to uni after I received my grades (PQA) (693)
41.08%
Yes, I like the idea of receiving offers only after I receive my grades (PQO) (338)
20.04%
I think there is a better option than the ones suggested (let us know in the thread!) (77)
4.56%