It has three times the atomic weight of hydrogen, because of the additional neutrons.

The additional neutron(s) may cause the nucleus to become unstable, causing it to decay (split) to form more stable products.

A compound nucleus may be formed, leading to additional neutrons being emitted more slowly.

Be + n 2α + 2n can contribute some additional neutrons in the beryllium neutron reflector of a nuclear weapon.

Instead of a sustaining chain reaction, a subcritical reactor uses additional neutrons from an outside source.

Tritium, a form of hydrogen with two additional neutrons in its nucleus, is especially vexing.

Another heavier version, or isotope, of sulfur contains two additional neutrons.

Pu-240 is produced when Pu-239 absorbs an additional neutron and fails to fission.

In the nucleus, additional neutrons are put in higher energy states until they have too high energy to be bound.

Electron capture in very dense parts of the infalling matter may produce additional neutrons.