Turn on thread page Beta

Effects of electronegativity on the bonding on an ionic compound? AgBr watch

    • Thread Starter
    Offline

    5
    ReputationRep:
    Hi guys,

    I was wondering if someone could please help me understand this concept.

    I have always understood electronegativity as the ability of an atom in a molecule to attract a pair of shared electrons towards itself. So this would usually have to be a covalent bond, as electrons would need to shared.
    I understand that differences in electronegativity can cause polarization in a covalent molecule, forming a dipole due to the uneven distribution of the shared electrons within the bond. (BTW would this be known as a polarised covalent bond?)

    But what impact could electronegativity have on an ionic compound? After all, ionic bonding involves electrons being transferred from a cation to an anion (and does not involve sharing).

    Could someone please explain to me how electronegativity could effect the bonding within an ionic compound and what effect it would have on a compound such as AgBr?

    Many thanks

    Evo
    Offline

    1
    ReputationRep:
    There is no pure ionic bonding. Ionic bonding is the extreme case of a polar covalent bond and you never get the electrons from the "cation" spinning around the nucleus of the "anion" 100% of the time. So, best think about ionic bonds as covalent bonds where electrostatic interactions are more important than molecular orbital interactions.

    The difference in electronegativities between Ag and Br is about 1, therefore the bond will be pretty polarised and is considered to be ionic. A rule of thumb - almost every compound which consists of a metal and a non-metal is going to be "ionic". There are a few exceptions but you needn't worry about them. By the way, although AgBr is an ionic compound, it is not soluble in water. Transition metals behave in strange ways and the drive to keep the lattice of this particular salt is bigger than the drive to break it and hydrate it (unlike NaCl, for example).

    I hope my answer wasn't too complicated and disorganised.
    Offline

    21
    ReputationRep:
    Is this from an AQA paper where the questions talks about theoretical 100% ionic bonding or something along the lines? Comparing AgCl and AgBr or something?

    If so then do not mention electronegativity as it is considered a chemical error, because electronegativity is about within a covalent bond.
    I had the same way of thinking as you until my teacher went through the question and told me never to write that if it's about ionic bonding..
    • Thread Starter
    Offline

    5
    ReputationRep:
    it may have originated from an old AQA paper but currently have it in an Access to science course assignment.
    Offline

    1
    ReputationRep:
    Electronegativity is not simply defined within a covalent bond, it is defined as unique to a particular element. Another rule of thumb would say that if the difference between two electronegativities is >1.7, the bond is ionic. However, our example is an exception, so is HF. You should see that the whole concept of electronegativity is a bit inexact in a sense.

    That there are no pure ionic bonds is not a way of thinking, it is a scientific fact. You can get free ions because of polarising solvents but without any side factors it is unfavourable to have two separate charges. I don't know what is considered "bad taste" in an exam, I am just posting rough-and-ready science. That's it
    Offline

    10
    ReputationRep:
    (Original post by 3vo)
    Hi guys,

    I was wondering if someone could please help me understand this concept.

    I have always understood electronegativity as the ability of an atom in a molecule to attract a pair of shared electrons towards itself. So this would usually have to be a covalent bond, as electrons would need to shared.
    I understand that differences in electronegativity can cause polarization in a covalent molecule, forming a dipole due to the uneven distribution of the shared electrons within the bond. (BTW would this be known as a polarised covalent bond?)

    But what impact could electronegativity have on an ionic compound? After all, ionic bonding involves electrons being transferred from a cation to an anion (and does not involve sharing).

    Could someone please explain to me how electronegativity could effect the bonding within an ionic compound and what effect it would have on a compound such as AgBr?

    Many thanks

    Evo
    The electronegativity of the cation in ionic solids is very important to their characteristics and has a very large impact upon the structure of the solid at the atomic level. Highly electronegative cations, i.e. Ti in TiO2 cause the bonds to have a significant degree of covalency to them so the atoms do not pack in the most efficient manner giving lower coordination numbers to the ions. By contrast the coordination number of Na and Cl in NaCl is higher as there is a much higher separation of charge between the ions.
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: March 30, 2014

University open days

  1. University of Bradford
    University-wide Postgraduate
    Wed, 25 Jul '18
  2. University of Buckingham
    Psychology Taster Tutorial Undergraduate
    Wed, 25 Jul '18
  3. Bournemouth University
    Clearing Campus Visit Undergraduate
    Wed, 1 Aug '18
Poll
How are you feeling in the run-up to Results Day 2018?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.