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    (Original post by Super199)
    Ah I was thinking something complicated for no reason. So oxidising agent is the one that is oxidised and reducing agent is the other one?
    Here is a concrete reaction with oxidation numbers.

    As you can see copper has a twice positive charge, after gaining two electrons, the charge was neutralized. By three gaining electrons, the charge would be negative (-1)!

    Iron has a neutral charge before losing electrons. After losing two electrons, the charge has got a twice positive charge. So note:

    an Oxidation decreases the oxidation number (getting more positive), but a reduction increases it (getting more negative).
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    (Original post by Super199)
    Gosh I'm confused now

    Care to give an example?
    I'll explain from scratch

    A species which is called an oxidising agent is a species which oxidises
    another species. The oxidising process is one where a species loses electrons.

    A species which is called a reducing agent is a species which reduces another species. This other species being reduced, is gaining electrons.

    Emphasis is on the fact whatever the agent is, the process it is named after is happening to another species, not itself. so a reducing species reduces another species, and thus itself is oxidised .

    an oxidating reagent oxidises another species, and thus itself must be reduced.

    for example

    Fe + Cu2+ --> Fe2+ + Cu

    In this process, two electrons have been lost from Fe, these two electrons are donated to the Cu2+, in order for that to form Cu. The Fe becomes Fe2+ (as it has lost two electrons)

    Therefore, Fe is the reducing species (it has donated electrons, electron gain has occured in the Cu). As a result of this donation, Fe has been oxidised (lost electrons).

    The Cu is the oxidising species (it has taken electrons from the Fe). In doing so, it has gained these electrons and therefore Cu itself has been reduced.

    The oxidising and reducing names come from the process the reagent is carrying out, thus the reverse process is actually happening to itself (think about the electrons being gained and lost in the processes)

    Hope this helps, you may need to read it a few times for it to click, but once it does you'll realise its quite an easy concept, it's just initially confusing.
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    (Original post by Super199)
    Gosh I'm confused now

    Care to give an example?
    use OILRIG where oxidation is loss and reduction is gain, so if a substance is oxidised, it's lost electrons and if it's reduced its gained electrons.

    An oxidising agent Oxidises something else

    A reducing agent Reduces something else

    If an oxidising agent oxidises something, it's taking electrons from it so it itself has gained those electrons, or is reduced. It's the other way around for the reducing agent, that reduces something else, or gives electrons to it and so is oxidised itself. Look at this equation

    Mg + Cu2+ ----> Mg2+ + Cu

    The magnesium goes from neutral to becoming 2+ so it's lost electrons, meaning it's been oxidised by Cu2+ so that's the oxidising agent. Those electrons that have been removed go to copper to form a deposit of copper, which has been reduced. Therefore Mg is the reducing agent because it gives electrons to Cu2+

    Hope that helps, best way to get your head around these is to practice.


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    I have a question on mass spectrometry.

    I've read that the technique can be used to determine the structure of an unknown compound but also to identify different isotopes of an element.

    If the spectra includes fragments, how are we to know if they are isotopes or just fragments? I'm sure I'm missing something in the mechanism of how this works, I'm having trouble visualising the process as a whole, thank you!!!
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    (Original post by Georgiam247)
    I have a question on mass spectrometry.

    I've read that the technique can be used to determine the structure of an unknown compound but also to identify different isotopes of an element.

    If the spectra includes fragments, how are we to know if they are isotopes or just fragments? I'm sure I'm missing something in the mechanism of how this works, I'm having trouble visualising the process as a whole, thank you!!!

    Is it because you only get fragmentation patterns in molecules? When looking at the spectra of an element you'd only get the isotope spectra cause the element can't be fragmented?
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    (Original post by Georgiam247)
    Is it because you only get fragmentation patterns in molecules? When looking at the spectra of an element you'd only get the isotope spectra cause the element can't be fragmented?
    In the mass spectrometer the molecule is split into fragments and the molecular ion.

    Take butane for example CH3CH2CH2CH3 there are two possible ways

    CH3CH2CH2CH3----> CH3+ + CH2CH2CH3•

    CH3CH2CH2CH3-----> CH2CH3+ + CH2CH3•

    Remember that the free radicals are uncharged so don't show up


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    Chemistry mock next wednesdayyyy!

    Haven't studied or done any chemistry for a very long time.
    Have started from the start.. Just recapping.

    I know this is awful, but I really don't know how to make up an equation.
    Like they give you the names of formula's.. say whats reacting with what. But I've realised idk how to write formula's lmfao :lolwut:

    help?
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    (Original post by Dinaa)
    Chemistry mock next wednesdayyyy!

    Haven't studied or done any chemistry for a very long time.
    Have started from the start.. Just recapping.

    I know this is awful, but I really don't know how to make up an equation.
    Like they give you the names of formula's.. say whats reacting with what. But I've realised idk how to write formula's lmfao :lolwut:

    help?


    Posted from TSR Mobile

    I also have an chemistry exam on Wednesday. Hopefully this link helps

    http://www.bbc.co.uk/schools/gcsebit...ntsrev11.shtml

    Do you think you can do well if you cannot even write equations at this latter stage? (Open question).
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    (Original post by Kadak)
    Posted from TSR Mobile

    I also have an chemistry exam on Wednesday. Hopefully this link helps

    http://www.bbc.co.uk/schools/gcsebit...ntsrev11.shtml

    Do you think you can do well if you cannot even write equations at this latter stage? (Open question).
    Does anyone know of any good notes on the internet for energetics (hess's law, enthalpy of formation etc)?
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    (Original post by Gladiatorsword)
    Does anyone know of any good notes on the internet for energetics (hess's law, enthalpy of formation etc)?
    I used this website http://chemrevise.org/revision-guides/ to revise for my Chemistry mock which I had today and found to be really useful, I didn't particularly use the energetics revision sheet but I can imagine it is helpful compared to the other stuff I used on there.
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    Im doing OCR
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    (Original post by Lollypop0)
    Im doing OCR
    That's on the website too


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    Need a little help understanding what happens to the ionic radius going across a period.
    I understand that it increases as you go down a group, because of the increase of protons, therefore extra shells (distance factor) and there is more shielding. But what happens across a period?

    I know what happens from e.g. Na- Al. The positive charge increases, therefore positive>negative. Hence, greater attraction between the electrons and the nucleus, making the ionic radius smaller.

    (Please tell me if i'm wrong, or if I've missed any details)

    But then from Si- Cl, the negative: positive charge is greater.. Therefore less attractive?? Idk :cry2:

    Pls help

    EDIT:

    Oh.. It's just because the number of protons increase across a period? Therefore greater nuclear attraction?

    Are ions down a period isoelctronic? Therefore from Na-Cl they are have the same number of electrons?

    OK, so if that is the case, then the protons(+) increase, whilst the electrons(-) stay the same. Causing positive>negative, therefore greater nuclear attraction!

    (please tell me that is right lmao, and if i've missed any details or whatever

    (Original post by zhang-liao)
    Edexcel
    [QUOTE=James A;52456081]I'm a 2nd year Pharmacy student at uni but I did Edexcel chem for A-levels and got an A.
    I'm stronger at organic chemistry than physical/inorganic chemistry it has to be said :lol:
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    (Original post by Dinaa)
    Need a little help understanding what happens to the ionic radius going across a period.
    I understand that it increases as you go down a group, because of the increase of protons, therefore extra shells (distance factor) and there is more shielding. But what happens across a period?

    I know what happens from e.g. Na- Al. The positive charge increases, therefore positive>negative. Hence, greater attraction between the electrons and the nucleus, making the ionic radius smaller.

    (Please tell me if i'm wrong, or if I've missed any details)

    But then from Si- Cl, the negative: positive charge is greater.. Therefore less attractive?? Idk :cry2:

    Pls help

    EDIT:

    Oh.. It's just because the number of protons increase across a period? Therefore greater nuclear attraction?

    Are ions down a period isoelctronic? Therefore from Na-Cl they are have the same number of electrons?

    OK, so if that is the case, then the protons(+) increase, whilst the electrons(-) stay the same. Causing positive>negative, therefore greater nuclear attraction!

    (please tell me that is right lmao, and if i've missed any details or whatever

    (Original post by James A)
    I'm a 2nd year Pharmacy student at uni but I did Edexcel chem for A-levels and got an A.
    I'm stronger at organic chemistry than physical/inorganic chemistry it has to be said :lol:
    It decreases across a period. If you go across let's say period 3 you'll see that the number of protons increases, however in terms of electrons they're being added to the same shield so you can say that the shielding remains the same. Because of the bigger nuclear charge and similar shielding, there's a greater electrostatic attraction between positive protons and negative electrons. These electrons are pulled more in towards the nucleus and so reducing the radius.

    Hope that helps


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    (Original post by Dinaa)
    Need a little help understanding what happens to the ionic radius going across a period.
    I understand that it increases as you go down a group, because of the increase of protons, therefore extra shells (distance factor) and there is more shielding. But what happens across a period?

    I know what happens from e.g. Na- Al. The positive charge increases, therefore positive>negative. Hence, greater attraction between the electrons and the nucleus, making the ionic radius smaller.

    (Please tell me if i'm wrong, or if I've missed any details)

    But then from Si- Cl, the negativeositive charge is greater.. Therefore less attractive?? Idk :cry2:

    Pls help
    Why am I quoted but Nvm.*Atomic radius.What's you describe for Na-Al is what should happen for all elements across since the beauty of the periodic table is that it shows trends which hold true for most elements.

    Remember, across a period,the electrons are added to the same shell,so electron shielding is similiar and so won't affect the positive charge that much.The increase in protons has is more important across the period than the increase in electrons.
    Hope this helps 😃.
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    (Original post by Dinaa)
    Need a little help understanding what happens to the ionic radius going across a period.
    I understand that it increases as you go down a group, because of the increase of protons, therefore extra shells (distance factor) and there is more shielding. But what happens across a period?

    I know what happens from e.g. Na- Al. The positive charge increases, therefore positive>negative. Hence, greater attraction between the electrons and the nucleus, making the ionic radius smaller.

    (Please tell me if i'm wrong, or if I've missed any details)

    But then from Si- Cl, the negative: positive charge is greater.. Therefore less attractive?? Idk :cry2:

    Pls help
    EDIT:

    Oh.. It's just because the number of protons increase across a period? Therefore greater nuclear attraction?

    Are ions down a period isoelctronic? Therefore from Na-Cl they are have the same number of electrons?

    OK, so if that is the case, then the protons(+) increase, whilst the electrons(-) stay the same. Causing positive>negative, therefore greater nuclear attraction!

    (please tell me that is right lmao, and if i've missed any details or whatever



    (Original post by James A)
    I'm a 2nd year Pharmacy student at uni but I did Edexcel chem for A-levels and got an A.
    I'm stronger at organic chemistry than physical/inorganic chemistry it has to be said :lol:


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    something confusing me about sterioisomers because my textbook doesnt make it very clear...
    With E/Z isomers i get that you compare atomic numbers
    My question is do you compare the entire atomic number of the whole group to the other side...or just invidivual atoms...for example

    chlorine on one side and CH15(just an example) on the other side
    Would you do Chlorine vs Carbon...chlorine wins....then chlorine vs hydrogen...so chlorine vs 15...chlorine wins so chlorine is the highest priority
    or would you do chlorine vs the entire atomic number of ch15 which would be like 21...which would be higher than chlorine so CH15 is higher priority
    thanks for any help
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    Posted from TSR Mobile

    Does anyone know any good websites/materials for isomers of alkenes revision?
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    (Original post by Dinaa)
    Need a little help understanding what happens to the ionic radius going across a period.
    I understand that it increases as you go down a group, because of the increase of protons, therefore extra shells (distance factor) and there is more shielding. But what happens across a period?
    As you go across the period, the IONIC radii increases because electrons are being added to the same shell so therefore the nuclear charge effect on individual electrons decreases, therefore the IONIC radii increases.

    I know what happens from e.g. Na- Al. The positive charge increases, therefore positive>negative. Hence, greater attraction between the electrons and the nucleus, making the ionic radius smaller.

    (Please tell me if i'm wrong, or if I've missed any details)
    Yep, that's pretty much right
    But then from Si- Cl, the negative: positive charge is greater.. Therefore less attractive?? Idk :cry2:

    Pls help
    I think you're trying to say that as you go across the period from Sillicon to Chlorine, more electrons are being added to the same shell (the 3p shell) so the positive charge on individual electrons is more shared and therefore the ionic radii decreases

    EDIT:

    Oh.. It's just because the number of protons increase across a period? Therefore greater nuclear attraction?
    Yep they do but when you're looking at ionic radii, you tend to look at the shells though and the electrons
    For ionisation energy, you look at electron shielding, proton charge (nuclear attraction) and the distance though
    Are ions down a period isoelctronic? Therefore from Na-Cl they are have the same number of electrons?
    If I remove 1 electron from Na, it is isoelectronic to Ne. If you ADD an electron to Cl so it gains a full electron config so it becomes isoelectronic to Ar
    OK, so if that is the case, then the protons(+) increase, whilst the electrons(-) stay the same. Causing positive>negative, therefore greater nuclear attraction!

    (please tell me that is right lmao, and if i've missed any details or whatever
    Across a period, protons increase and electrons stay on the same shell though (but the electron number DOES however increase). This causes the nuclear attraction to be more equally shared on individual electrons
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    (Original post by Kadak)
    Posted from TSR Mobile

    Does anyone know any good websites/materials for isomers of alkenes revision?

    Chem guide
 
 
 
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