Nuclear Binding Energy and Nuclear Force

Nuclear Binding Energy

• The nucleus of an atom cannot exist according to classical electrostatic theory due to the repulsive force among protons.
• The stability of the nucleus is explained by the existence of a strong binding force called the nuclear force.
• The nuclear force overcomes the repulsive force of protons and is effective equally among all nucleons.
• The nuclear force only exists within the nucleus and has no influence outside.
• The short range of the nuclear force leads to a small nucleus size (~10⁻¹³ cm) and high density (~10¹⁴ g/cm³).

Mass Defect and Binding Energy

• The mass M of a nucleus is always less than the combined masses of the nucleons A.
• The difference in mass (MA) is termed the mass defect, which is used as binding energy for all nucleons in the nucleus.
• The average binding energy of a nucleon is equal to the total binding energy divided by the number of nucleons.
• The average binding energy of a nucleon is of the order of 6-9 MeV.
• Binding energy of an individual nucleon has a definite value depending on the shell it occupies.

Comparison with Electron Binding Energy

• Binding energy of nucleons is in the megaelectron volt (MeV) range.
• Electron binding energy in the atomic orbital is of the order of kiloelectron volts (keV), a factor of 1000 lower.

Nuclear Nomenclature

• A nuclide is defined as an atomic species with a specific number of protons and neutrons arranged in a definite order in the nucleus.

Radionuclides

• Radionuclides are unstable nuclides that decay by emitting particles, electromagnetic radiations, or through spontaneous fission.

Isotopes

• Isotopes are nuclides with the same atomic number (Z) but different mass numbers (A).
• Isotopes exhibit the same chemical properties.
• Examples of isotopes: 11C, 12C, and 13C (all carbon isotopes).

Isotones

• Isotones are nuclides with the same number of neutrons but different numbers of protons.
• Examples of isotones: Cs, Xe, and 53I, each having 79 neutrons.