Musing idly, as I often do, I have wondered if, in this age of subatomic beasties and particle accelerators, we could in theory turn lead into gold. One day last summer, having nothing better to do than send frivolous emails to people who are busier than I am, I asked a few acquaintances who might be interested -- including the only physicist I know -- what they thought about it.
The physicist said:
I looked up images of the periodic table.
The gold nucleus has 79 protons and an average of (197-79=118) neutrons.
The lead nucleus has 82 protons and an average of (207-82=125) neutrons.
I suppose the way to turn lead into gold is to knock 3 protons out of the lead nucleus, probably by bombarding lead with neutrons (which have no charge, so will not be repelled by the charged lead nucleus).
As you can see, this process requires a source that emits neutrons. Pretty expensive.
I am not a nuclear physicist, so that is the best I can do.
The most complete answer came from a software developer -- not a nuclear physicist either, but keenly interested in physics and possessed of a book that related to the subject. He explained how in theory lead could be converted to gold: You would take your lump of lead and bombard it with neutrons, and an atom here and there would trade its leaden identity for a second career as a different element.
The name of the new element began with B. A search of my mental file of elements turned up six of that description. I know all the elements as of about 1960, thanks to Tom Lehrer's brilliant mnemonic (https://www.youtube.com/
Bromine is a gas; beryllium and boron sound like minerals; barium is an alkaline earth metal (whatever that is); and berkelium must be one of those temporary manufactured elements that last three quarters of a second before decaying into something else. Bismuth, like gold and lead, is a metal (with 83 protons and 126 neutrons); it's also a decay product of lead. Lets go with bismuth, and thank you, Wikipedia.
My son reminded me that converting one random atom at a time would produce a highly variegated lump of matter. With that in mind, you would bombard your piece of lead until you had a workable amount of bismuth with residual lead, assorted impurities, and presumably a bit of gold from atoms that got in the way twice. You would then refine it so as to have bismuth and not much else.
The software developer's wife pointed out that the lump would be radioactive as hell. The gold, responded he, wouldn't be radioactive because gold doesn't do that; but, yes, the lead and bismuth and impurities would be dangerous to have around. Be that as it may - after refining your newly produced bismuth, you would bombard it again and refine it a second time. You would then have a small nugget of gold that you could display in a museum with a label explaining its origins.
I can't imagine who in this world would have the time and money to expend on any such piece of whimsy. I wonder how difficult it would be to explain to Paracelsus and the rest of them that we have at last achieved their age-old goal but that the process is so expensive it isn't worth doing. We might find ourselves, like Mark Twain's Connecticut Yankee explaining basic economics to King Arthur's subjects, shouting across an insurmountable barrier of paradigm shifts.
