Symbol

Pa

Atomic Number

91

Atomic Mass

231.03588

Family

Actinide Pronunciation

pro-tack-TIN-ee-um

Overview

Protactinium is one of the rarest elements on Earth. It is formed when uranium and other radioactive elements break down. For many years, the only supply of protactinium of any size was kept in Great Britain. The British government had spent $500,000 to extract 125 grams (about four ounces) of the element from 60 tonnes (60 tons) of radioactive waste. Relatively little is known about the properties of the element, and it has no commercial uses.

Protactinium belongs in the actinides series in the periodic table. The periodic table is a chart that shows how chemical elements are related to one another.

Discovery and Naming

Scientists first learned about radioactive elements toward the end of the nineteenth century. Radioactive elements are elements that break apart all by themselves. They give off radiation— somewhat similar to light or X rays—and change...