## Nuclei – Class 12 | Chapter – 13 | Physics Short Notes Series PDF for NEET & JEE

Nuclei: In physics, nuclei refer to the central part of an atom that contains protons and neutrons. The nucleus is the most massive and dense part of an atom and it makes up almost all of the atom’s mass. Electrons orbit around the nucleus in shells or energy levels, but they contribute very little to the total mass of the atom.

The number of protons in the nucleus determines the atomic number of the element, while the number of neutrons determines the isotope of the element. Nuclei can undergo various types of nuclear reactions, such as radioactive decay, fusion, and fission, which can release large amounts of energy.

The study of atomic nuclei is a branch of physics called nuclear physics, which seeks to understand the properties and behavior of atomic nuclei, as well as the interactions between nuclei and other particles. This field has important applications in energy production, medical imaging and treatment, and fundamental research in particle physics.

## Density of Nuclei Matter

The density of atomic nuclei matter varies depending on the element in question. However, in general, atomic nuclei matter is extremely dense, much denser than the density of ordinary matter that we encounter in our daily lives.

The density of atomic nuclei matter is typically measured in terms of nuclear density, which is defined as the mass of a nucleus per unit volume. The nuclear density is typically expressed in units of grams per cubic centimeter (g/cm3). For example, the nuclear density of a typical atomic nucleus is around 2.3 x 1017 g/cm3.

To put this into perspective, the density of ordinary matter such as water is about 1 g/cm3, while the density of a neutron star, which is composed of tightly packed atomic nuclei, can be several times greater than the nuclear density of an individual atomic nucleus.

The high density of atomic nuclei matter is a result of the strong nuclear force, which is the force that binds the protons and neutrons in the nucleus together. This force is much stronger than the electromagnetic force that governs the behavior of electrons and is responsible for the relatively low density of ordinary matter.

## Properties of Nuclei Matter

The properties of nuclei matter depend on various factors, such as the number of protons and neutrons in the nucleus, the energy of the nucleus, and the environment in which the nucleus exists. Some of the key properties of nuclei matter are:

• Mass: The mass of a nucleus is determined by the number of protons and neutrons it contains. The mass is expressed in atomic mass units (amu), where one amu is equal to 1/12th the mass of a carbon-12 atom. The mass of a nucleus is much greater than the mass of the electrons in the atom, so it is a major contributor to the overall mass of the atom.
• Charge: The charge of a nucleus is determined by the number of protons it contains. Since protons have a positive charge, the nucleus has a net positive charge. The number of protons in the nucleus determines the atomic number of the element, and elements with different atomic numbers have different chemical properties.
• Stability: The stability of a nucleus depends on the balance between the strong nuclear force, which binds the protons and neutrons together, and the electromagnetic force, which tends to push the positively charged protons apart. Nuclei that are unstable may undergo radioactive decay to become more stable.
• Energy: Nuclei can have different levels of energy, which can be expressed in terms of their excitation energy or their binding energy. Nuclei can absorb or release energy through various types of nuclear reactions, such as fusion, fission, or radioactive decay.
• Spin: Nuclei have a property called spin, which is related to their angular momentum. The spin of a nucleus can affect its interactions with other particles and can be used to study the structure of the nucleus.

The properties of nuclei matter have important implications for a wide range of fields, including nuclear physics, astrophysics, and nuclear engineering.

 JOIN OUR TELEGRAM CHANNELS Biology Quiz & Notes Physics Quiz & Notes Chemistry Quiz & Notes 