Early 20th

15 elements

The first artificially produced element. All isotopes are radioactive, none are ...

Named after the dwarf planet Pluto, following the uranium-neptunium-plutonium se...

The only radioactive lanthanide with no stable isotopes. Barely half a kilogram ...

Named after Europe, just as americium would later honor the Americas. The most r...

The last and hardest lanthanide, named after Lutetia, the Roman name for Paris, ...

Named after Hafnia, the Latin name of Copenhagen, and found exactly where Bohrs ...

The last stable element ever discovered, named after the Rhine river. Rhenium ke...

The rarest naturally occurring element on Earth. At any moment the entire planet...

A radioactive gas that seeps from soil and rock into basements, and the second l...

The most unstable of the first 101 elements: no francium atom survives longer th...

The name means parent of actinium, which it becomes through radioactive decay. O...

The first element beyond uranium ever created, named for the next planet out, fo...

Sits in nearly every home, invisibly: a speck of americium-241 in a smoke detect...

Named for Pierre and Marie Curie, honoring the study of radioactivity. So intens...

Named for Berkeley, California, home of the cyclotron that made it. Produced by ...