noun
- a radioactive metallic chemical element with the symbol Pa and atomic number 91
Usage: chemistry
Examples
- Protactinium is one of the rarest naturally occurring elements on Earth.
- The scientist studied the radioactive decay of protactinium isotopes.
- Protactinium was first identified in uranium ore samples.
- The element protactinium has a very short half-life.
- Researchers handle protactinium with extreme caution due to its radioactivity.
- Protactinium appears in the actinide series of the periodic table.