[plu]

Is it true that the dG_f^o for all elements in their standard states is a positive value?  Checking up on a table of standard free energy of formation values seems to agree with this idea.  However, I don't quite understand how/why this is so.  Any ideas?

[jdurg]

Try and remember how dGf is calculated.  It uses the equation dGf = dHf -T(dSf).  So the free energy of formation is equal to the heat of formation - the entropy of formation times the temperature.  The Enthalpy of Formation of an element in its standard state is ALWAYS zero.  The entropy of formation of an element in it's standard state is a negative value as well.  (Since you are taking random, disordered subatomic particles and forcing them into an ordered arrangement, so the entropy decreases).  If you look at the equation, the right hand side (T(dSf)) will always be a negative value.  Zero minus a negative value is ALWAYS a positive value.  Hence the dGf for all elements in their standard states is positive.