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Thread: Dissociation vs ionization?

  1. #1 Dissociation vs ionization? 
    Forum Sophomore
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    I searched the web but I still don't get the differences between them.


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  3. #2  
    exchemist
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    As far as I recall, dissociation refers to a molecule or ionic lattice separating into complementary cations and anions.

    Ionisation on the other hand refers to the process of removing an electron from an atom or molecule.

    So, when you dissolve salt in water, it dissociates into Na+ and Cl- ions. And vinegar contains partially dissociated acetic acid: CH3COOH <-> CH3COO- + H+.

    When you irradiate Na atoms with enough light of the right frequency, you ionise it to Na+, which means an electron gains enough energy by absorption to escape from the atom completely.

    Ionisation typically needs a lot more energy than dissociation, as an electron is removed "to infinity", while with dissociation an electron either does not move at all (as with ionic solids) or if it does (as with covalent molecules) it just moves, from an atom that is willing to lose it, to an atom that is willing to accept it, thus forming a pair of ions.


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  4. #3  
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    Ionisation, or ionisation is the energy needed for the outer electron of an atom to reach n=infinity which means that electron leaves the atom as it has achieved an excited state. Therefore ionisation energy is the energy needed to "remove" an electron from an atom.

    Dissociation, or dissociation energy is the energy needed to "break" a molecule or ionic lattice to form the negative and positive ions (cations and anions).
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