The high binding energy of iron refers to the energy holding together
the particles in the nuclei of iron atoms. Saying that iron is stable
means that it would take relatively a lot of energy to create a
nuclear reaction such as fusion or fission with iron atoms, compared
to other elements.
Chemical reactions are different from nuclear reactions--nuclear
reactions involve much higher levels of energy, and nuclear reactions
involve changes in the nuclei of atoms, whereas chemical reactions
don't change nuclei, but just change the way atoms are hooked together
with chemical bonds, which involve electrons rather than nuclei.
Because the nucleus determines the atom's identity as an element,
after a nuclear reaction, iron would not be iron any more, whereas
after a chemical reaction, iron atoms would still be iron atoms, just
arranged in molecules differently.
So iron's reluctance to participate in nuclear reactions is unrelated
to its willingness to participate in chemical reactions and you are
correct that nuclear stability is different from chemical inertness."
the binding energy of iron relates to it nucleus while it 's ability
to react to other chemical elements has more to do with its overall
atomic structure. (Most importantly the distribution and energy levels
of the electrons which are associated with the iron atom). Unlike
elements such as Helium and Argon, Iron
is certainly not a chemically inert element.
The 'stability' to which you refer is thus closely associated with the
nucleus. When an iron nucleus or any atom with an atomic number less
than iron disintegrates , it takes an excess of energy to do this.
However when nucleii of atoms with greater atomic number than iron
disintegrate then there is an 'excess' of energy. (the best examples
been atoms of Uranium and Plutonium) which emit large amounts of
energy when their nucleii disintegrate.
It should also be pointed out that most nucleii of atoms are normally
stable and it takes an outside interation to cause it to split or
disintegrate. (In the case of Plutonium and Uranium it is usually the
absorption of an neutron into its nuclues)
