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    We always said the lattice disassociation enthalpy assume the molecule is fully ionic with no convalent character , however if a molecule contain convalent character . What will the enthalpy like compare with the therotical one ? Less or more ?
    Moreover , how is the boiling point stuff related to the enthalpy . What kind of bond are we breaking in enthalpy ? Is it just the bond or intermolecular force ? When a ionic compound becoming more convalent character . How does the lattice disassocaiation enthalpy change ? More or less .
    At last , does enthalpy change of formation is the net enthalpy change of breaking bond and making bond ?
    Does it mean that it doesnt has to be negative all the time . It can be positive .

    Somebodyyy please help ;
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    I'm not sure if there is a definite answer that fits all. I think for some structures - having covalent character makes it stronger so the lattice enthalpy of dissociation would be higher. For other structures it makes the lattice enthalpy of dissociation lower - Al2O3 for example breaks the period 3 metal oxide boiling point pattern - due to this covalent character.
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    (Original post by B_9710)
    I'm not sure if there is a definite answer that fits all. I think for some structures - having covalent character makes it stronger so the lattice enthalpy of dissociation would be higher. For other structures it makes the lattice enthalpy of dissociation lower - Al2O3 for example breaks the period 3 metal oxide boiling point pattern - due to this covalent character.
    There are two distinct 'types' of covalent character: one leading to giant covalent and the other leading to simple covalent.

    All you can do is use empirical evidence to compare experimental lattice enthalpy with theoretical to decide if the ionic character is being compromised.
 
 
 
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