Edexcel ial chemistry unit 2 june 2018 discussion & predictions

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E.143.G
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Hi all,

does anyone have any predictions on the upcoming unit 2 paper?

we can also have questions/topics discussions on here
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Stressed4ever
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Hello there,
I have a question on redox reactions and writing half equations. Here’s an example:
MnO4- + Fe2+ -> Mn2+ + Fe3+
Am I supposed to add the H+ on the side where O is most and H2O where it is not? And does it always go that way?
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Miral_hos
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I was going through the specification and saw “demonstrate an understanding of the link beween bond polarity and the type of reaction mechanism a compound will undergo.” If anyone’s got a good summary for this, please help a sis )
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E.143.G
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(Original post by Miral_hos)
I was going through the specification and saw “demonstrate an understanding of the link beween bond polarity and the type of reaction mechanism a compound will undergo.” If anyone’s got a good summary for this, please help a sis )
A polar molecule will react differently than a non-polar molecule
  • eg. C-H will react differently to C-C
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username3718068
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(Original post by Stressed4ever)
Hello there,
I have a question on redox reactions and writing half equations. Here’s an example:
MnO4- + Fe2+ -> Mn2+ + Fe3+
Am I supposed to add the H+ on the side where O is most and H2O where it is not? And does it always go that way?
Solve by Treating each half eqn separately, rather than trying to solve by writing the overall eqn.
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yeswhynot76
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Guys please make this group alive and discuss
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nano-deverdad
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guys do you know why the covalent bond in ICL3 has two lone pairs?
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::mellOddy::
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(Original post by nano-deverdad)
guys do you know why the covalent bond in ICL3 has two lone pairs?
Iodine sits in group 7, thus contains 7 valence electrons. Iodine makes 3 bond pairs with the three chlorine atoms. This leaves 4 electrons (which aren't involved in bonding) or 2 lone pairs.
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nano-deverdad
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so basically they dont always follow the octet rule right?
and how do u know if the octet rule is followed or not ?
thank you so much such a life saverrrr
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nano-deverdad
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(Original post by ::mellOddy::)
Iodine sits in group 7, thus contains 7 valence electrons. Iodine makes 3 bond pairs with the three chlorine atoms. This leaves 4 electrons (which aren't involved in bonding) or 2 lone pairs.
sirry forgot to tag you the first time
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::mellOddy::
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(Original post by nano-deverdad)
so basically they dont always follow the octet rule right?
and how do u know if the octet rule is followed or not ?
thank you so much such a life saverrrr
True, the octet rule is not always followed. The most common form of exception to the octet rule is "expansion". like in the ICl3 question. (iodine expands from 8 valence electrons to 10).

To know why here the octet is being expanded/ octet rule not being followed, simply draw all the valence shell electrons of the central atom. ( careful with molecular ions here. A molecule with +1 charge can mean one less electron in the outer shell and vice versa). once the valence electrons are drawn, arrange the surrounding atoms around the central atom ( making single double or triple bonds - whatever gives the 'surrounding atom' a complete octet. once all the surrounding atoms are sharing electrons and have complete octets, any remaining electrons of the central atom that weren't used in bonding are lone pairs.

few things to remember:
Expanded valence shells are only observed for period 3 elements.
s (2 electrons)and p(6 electrons) orbitals are the ones being used for the octet rule. when the octet is expanded it means the vacant d subshells are being used. ( d subshells have 10 electrons..notice how iodine expands to have 10 electrons too? d subshells being used). questions related to d subshell are very common in past papers too.

check out the specification of unit 2. it states all the types of molecular ions and molecules you need to know for the first topic in unit 2.
hope that helps
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nano-deverdad
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omg thank you sooo much literally so helpful can u send me the link for the specification if you have it literally thank you so much so useful i cant believe how much this helped me.
so basically only period 3 elements can extend above the octet rule right?
(Original post by ::mellOddy::)
True, the octet rule is not always followed. The most common form of exception to the octet rule is "expansion". like in the ICl3 question. (iodine expands from 8 valence electrons to 10).

To know why here the octet is being expanded/ octet rule not being followed, simply draw all the valence shell electrons of the central atom. ( careful with molecular ions here. A molecule with +1 charge can mean one less electron in the outer shell and vice versa). once the valence electrons are drawn, arrange the surrounding atoms around the central atom ( making single double or triple bonds - whatever gives the 'surrounding atom' a complete octet. once all the surrounding atoms are sharing electrons and have complete octets, any remaining electrons of the central atom that weren't used in bonding are lone pairs.

few things to remember:
Expanded valence shells are only observed for period 3 elements.
s (2 electrons)and p(6 electrons) orbitals are the ones being used for the octet rule. when the octet is expanded it means the vacant d subshells are being used. ( d subshells have 10 electrons..notice how iodine expands to have 10 electrons too? d subshells being used). questions related to d subshell are very common in past papers too.

check out the specification of unit 2. it states all the types of molecular ions and molecules you need to know for the first topic in unit 2.
hope that helps
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::mellOddy::
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(Original post by nano-deverdad)
omg thank you sooo much literally so helpful can u send me the link for the specification if you have it literally thank you so much so useful i cant believe how much this helped me.
so basically only period 3 elements can extend above the octet rule right?
No problem.
here's the spec. save you some time, go straight to page 25.
Oh and yes only period 3 elements can EXTEND their octet
https://qualifications.pearson.com/c...istry-Spec.pdf
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nano-deverdad
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(Original post by ::mellOddy::)
No problem.
here's the spec. save you some time, go straight to page 25.
Oh and yes only period 3 elements can EXTEND their octet
https://qualifications.pearson.com/c...istry-Spec.pdf
once again thank you so much like actually such a lifesaver and good luck for unit 2 wish you all the best
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nano-deverdad
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are you sure its on page 25 tho? cant seem to find it
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::mellOddy::
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(Original post by nano-deverdad)
are you sure its on page 25 tho? cant seem to find it
Um yes, i'm on page 25 of 108
3C shape of molecules
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MARYAM1234567
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hello everyone!
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laishafaheem
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(Original post by nano-deverdad)
so basically they dont always follow the octet rule right?
and how do u know if the octet rule is followed or not ?
thank you so much such a life saverrrr
What is the octet rule?
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::mellOddy::
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when elements react they tend to do so in a way that results in an outer shell containing 8 electrons. a full octet gives the atom its stability.
(Original post by laishafaheem)
What is the octet rule?
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laishafaheem
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(Original post by ::mellOddy::)
when elements react they tend to do so in a way that results in an outer shell containing 8 electrons. a full octet gives the atom its stability.
Thank you!
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