Because energy is released when you remove atom parts. 
I was writing a book/screenplay about this…
Transmutation.
"A guy attempting to create a free power device using magnets, shielded the dynamo in a lead lined container, because of stray microwaves.
When a storm rolled through, the device was struck by lightning, resulting in the lead to transmute to gold.
So, he starts selling the gold to pawn shops, in small amounts and they in turn make jewelry and sell to people.
But, the gold has an extra electron and thus is radioactive, and is being detected in airport security scanners.
The Government Scientist finds out whats going on and then try to find the source through Homeland Security. Which of course has an operative that leaks the information to the Evil Country. (plot device)
Now the guy is on the run from both the Good Guys and the Bad guys who both want the secret to Transmutation.
Eventually a Scientist discovers that the Radioactive gold isn’t stable and it splits into two other atoms that cause a lot of explosions from particle decay. So the good guys now are in a massive search to thwart the eventual Big Badda Boom.
Now the bad guys found the main character and retrieve the initial stock pile of Radio active gold and set of to their homeland in a military plane, in which they have no clue that the mass of fake gold has just reached critical mass and explodes safely over the middle of the Pacific Ocean. Killing all on board.
Department of Homeland Security files the paperwork and stuffs it all in a “Top Secret” envelope into a file cabinet in a vast hall of filing cabinets full of top secret stuff.
In the end, the Main Character is shown playing with a couple of magnets and just tosses them in a drawer in a cabin where he is under federal witness protection."
*I know this isn’t real science…just close enough to be a decent movie. 