Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How to combine elements of differing ionic charge

  1. Jan 7, 2005 #1
    It's easy when say zinc is +2 and chloride is -1, so it is ZCL2

    However, say I wanted to combine say, oxygen and gold. Gold has +1 and +3 and oxygen is -2, which of the gold do I use? (+1 or +3, for example)
  2. jcsd
  3. Jan 7, 2005 #2


    User Avatar

    I believe you can use both. [tex]AuCl_3[/tex][tex]AuCl[/tex] They are different compounds of gold. Alot of transition metals have more than 1 charge.

    o ya, I used chlorine because gold is not very reative, only with chlorine and fluorine. :approve:
  4. Jan 7, 2005 #3


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    As DB's said already, elements that exhibit multiple valency form more than one compound with another element (as long as the two will react). The dominant valency leads to the more stable compound. Less favored valencies (or oxidation states) result in less stable, or more reactive compounds.

    In tha case of Au, the +3 state is much more stable than the +1 state (the reason for this is a little complicated). But gold itself is quite an unreactive metal, so it will react only with the most electronegative elements like the halogens (F, Cl, Br, I) and the chalcogens (O, S, Se, Te).

    Since the +3 state is preferred, compounds like AuF3, AuCl3, AuBr3, Au2O3 are quite stable. However, AuCl, AuBr, Au2O also exist, though they are less stable. But when you get to the bigger atoms (Se, I), it becomes difficult to squeeze 3 of these around a gold atom. The repulsion between these atoms (also known as steric hindrance) becomes very strong. So, with the bigger atoms, the +1 state is preferred, and so, in these cases AU2Se and AuI are the more stable compounds.

    This is just a crude explanation, and the details are far more complex. But the general lesson to be learned is that, when an element exhibits multiple valencies (this is particularly pronounced with the d-block, or transition metals), it will form multiple compounds with another element, their stabilities generally depending on the dominance of the valency.
    Last edited: Jan 7, 2005
  5. Jan 7, 2005 #4


    User Avatar
    Science Advisor
    Homework Helper

    To add a little,the maximum oxydation states is usually realized in fluorides,as the fluorine is the most rectiv nonmetal,plus it has the 'smallest' molecule among the halogens.It sometimes occurs with the oxygen,too.
    E.g.Xe (54) has the oxydation states:+2,+4,+6,+8.The maximum one is encontered in the octofluorine:[itex] XeF_{8} [/tex] and the tetraoxyde:[itex] XeO_{4} [/itex].

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?