Negative entropy value for F- (aq) and OH-(aq)?

AI Thread Summary
The discussion centers on the observation of negative standard entropy (S°) values for the ions F- (aq) and OH- (aq) while studying thermodynamic properties of various substances. The key point is that a negative entropy value indicates a decrease in disorder when transitioning from gaseous fluorine (F2) to aqueous fluoride (F-), suggesting that the formation of these ions leads to a more ordered state. The conversation explores the implications of negative entropy for ions, questioning why only F- and OH- exhibit this property and considering factors such as electronegativity. The underlying principle is that certain reactions can result in lower entropy due to the nature of the reactants and products involved.
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I'm currently studying thermodynamics, and while looking through the chart of \Delta H\circ, S\circ, and \Delta G\circ values for 200+ substances. Out of these, I noticed that two (F- (aq) and OH- (aq) have a negative S\circ value. How can a single ion have a negative entropy? I understand that irreversible rxns and rxns with more moles of product than reactants have a negative S\circ value, but I am having trouble seeing a negative entropy value for an ion. And why just F- and OH-? What makes them special? Electronegative? (For F- at least..)?

Thanks.
 
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Your table most likely lists values for the standard formation enthalpies and entropies. A negative So value just means that going from F2(g) to F-(aq) involves a decrease of entropy.
 

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