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Nucleus composition
Beginner
Protons and neutrons make up nuclei.
A nucleus has Z protons and N neutrons (A = Z + N nucleons). Notation ᴬ_Z X. Protons determine the element.
Carbon-14: Z = 6, N = 8.
Neutrons give stability and isotopes.
In more detail
The atomic nucleus contains protons and neutrons, held together by the strong nuclear force. The number of protons gives the element, and the total number of nucleons gives the mass number.
Real-world uses
- Nuclear medicine uses specific isotopes based on their nucleon numbers.
- Nuclear reactors use nuclei with particular compositions.
- Physicists describe nuclei by their numbers of protons and neutrons, which determine their identity and stability.
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Frequently asked questions
What is the mass number?
The total number of protons and neutrons in the nucleus.
How big is the nucleus?
Around a few femtometres, far smaller than the atom.
Are all nuclei made only of protons and neutrons?
For ordinary matter, yes. Exotic exceptions exist, but protons and neutrons make up virtually all atomic nuclei.
Related topics in Atomic & Nuclear Physics
X-ray diffraction · Electron configuration · Atomic mass unit · Isotopes, isobars, isotones · Nuclear size · Nuclear density