The synthetic (or man-made) elements are the ones with silly-sounding names, found along the bottom of the periodic table — Einsteinium and Nobelium, Livermorium and Mendelevium, and more. Unlike the rest of the elements, you won't find them just hanging out in nature. They have to be created in a laboratory, and they only exist for a limited amount of time — some no more than milliseconds. Though new ones have been discovered/created as recently as 2010, the 1950s and 60s were sort of a heyday of synthetic elements, with different laboratories locked in a race to find the niftiest new things first.
During that time, researchers at Lawrence Berkeley National Lab made a film strip reenacting their own 1955 discovery of the element Mendelevium. The film lay forgotten in storage for 60 years until it was recently uncovered and restored by retired physicist Claude Lyneis. Originally just a silent sequence showing real Mendelevium discoverers Al Ghiorso, Bernard Harvey, Gregory Choppin, and Stanley Thompson demonstrating how they'd found the 101st element, the film has been updated with narration and sound effects and is a pretty cool explanation of where synthetic elements come from.