Nucleus

How it is used

The plural is 'nuclei'. Protons and neutrons together are called nucleons. A nucleus is described by its proton number (atomic number, Z) and nucleon number (mass number, A). Nuclear physics studies how nuclei decay, split and fuse.

Example sentences

1. A carbon-12 nucleus contains six protons and six neutrons.

2. Most alpha particles went straight through the gold foil, which showed that the nucleus is tiny.

Common collocations

• atomic nucleus
• stable nucleus
• unstable nucleus
• strong nuclear force
• daughter nucleus

Related terms

• atomThe smallest unit of a chemical element, made of a tiny positive nucleus surrounded by negatively charged electrons. Most of an atom is empty space.
• isotopeOne of two or more forms of the same element whose atoms have the same number of protons but different numbers of neutrons. Isotopes behave the same chemically but have different masses.
• radioactive decayThe random process in which an unstable nucleus breaks down by giving off radiation, such as alpha particles, beta particles or gamma rays, and often turns into a different element.
• nuclear fissionThe splitting of a heavy nucleus, such as uranium-235, into two smaller nuclei, usually after it absorbs a neutron. It releases a large amount of energy and more neutrons.
• nuclear fusionThe joining of two light nuclei, such as isotopes of hydrogen, to form a heavier nucleus. It releases huge amounts of energy and is what powers the Sun and other stars.

This word in other fields

The same English word can have a different meaning in another field:

• nucleus · Anatomy & Physiology
• nucleus · Biology

More terms: Atomic and Nuclear Physics

• electron
• half-life