A stable electron configuration has 8 valence electrons and a full octet, meaning that their would be a "happy" atom and it would be non reactive.
Chemical change. You can never get back the rusted layers of metal even though you can wipe off the rust. Chemical changes are irreversible.
Bonjeur monseur, la french are here! it seems you have a problem with the elements on earth. lead seems correct since it is indeed a harmful material
The answer to this question will be Uranium
