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

Null_

I'm currently studying thermodynamics, and while looking through the chart of [tex]\Delta[/tex] H[tex]\circ[/tex], S[tex]\circ[/tex], and [tex]\Delta[/tex] G[tex]\circ[/tex] values for 200+ substances. Out of these, I noticed that two (F- (aq) and OH- (aq) have a negative S[tex]\circ[/tex] 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[tex]\circ[/tex] 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.

espen180

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