Symbol

Np

Atomic Number

93

Atomic Mass

237.0482

Family

Actinide Transuranium Element Pronunciation

nep-TOO-nee-um

Overview

Neptunium lies in Row 7 of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Neptunium is the first transuranium element. The term transuranium means "beyond uranium." Any element with an atomic number greater than 92 (uranium's atomic number) is called a transuranium element. Elements in Row 7 are also called actinide elements. This name comes from the first element in Row 7, actinium.

Scientists have now found about 18 isotopes of neptunium. They are all radioactive. Neptunium was once a very rare element, but it can now be somewhat easily produced in a nuclear reactor. A nuclear reactor is a device in which nuclear fission reactions occur. Nuclear fission is the process of splitting atoms when neutrons collide with atoms of uranium or plutonium. These collisions produce new elements...