Differentiate between a single atom of gold and a single atom of lead. (no multiple choice)

Lead has a different chemistry than most biological metals, but it can mimic some of them, such as calcium, iron, and zinc, because it tends to form 2+ ion like other metals, and these can be formed inside the body. Due to it different chemistry, lead prevents normal functioning of the enzymes it binds to, inhibiting them and poisoning the body.

Gold rarely forms ions, unless under extreme conditions that are not present in the human body. Gold ions, when ingested, are actually very toxic, so gold poisoning is possible. But because gold are so rare, gold poisoning is also a rare phenomenon.