Lead to gold transmutation While reading answers to the Were alchemist right?, I have come across the answer by @AndrewSteane. All in all he claims:

But the idea that it might be possible to transform one chemical
element into another is not at all a stupid idea. It is a perfectly
sound idea. However it turns out that it requires processes that
change the atomic nucleus, and this requires either the use of
radioactivity or else high-energy collisions. It cannot be done by
chemical reactions. So no amount of heating stuff up in ordinary fires
or pouring one liquid into another or adding ingredients of this or
that is going to work.

Now, I am not a physicist, but in my completely unrelated field the question "if something is possible by applying this and that" is orders of magnitude harder than just "I have done this and that and produced desired something".
How do we know that

no amount of heating stuff up in ordinary fires
or pouring one liquid into another or adding ingredients of this or
that is going to

actually transmute one element into another?
 A: Here is why.
All the heating we can do in chemistry labs, and all of the chemical reactions we can produce there, only affect the particulars of the outermost portions of the electron clouds that surround the nuclei. This fact is well-known and furnishes the fundamental basis for the entire field of chemistry. Chemical processes that involve heat like this are from first principles insufficiently energetic to alter in any way the particulars of the innermost electron clouds or for that matter the composition of the nucleus itself.
Any process that purports to do so is required to be energetic enough to completely penetrate those electron clouds and interact directly with the nucleus. This requires millions of times the energies typical of chemical processes and cannot be achieved by any heat source in any chemical lab. Applying those magnitudes of  thermal energy to a bulk sample of atoms results in stripping the electron clouds away from them in their entirety, at which point the resulting fully-ionized nuclei are fundamentally incapable of participating in chemical processes, because their electrons are gone.
