## Size of the Nucleus – Class 12 | Chapter – 13 | Physics Short Notes Series PDF for NEET & JEE

Size of the Nucleus: The size of the nucleus depends on the number of protons and neutrons it contains. The nucleus is typically much smaller than the overall size of the atom, with a diameter that is on the order of 10-15 meters.

## Size of the Nucleus – Rutherford Gold Foil Experiment

The Rutherford gold foil experiment was a groundbreaking experiment conducted by Ernest Rutherford and his colleagues in 1910, which helped to establish the modern understanding of the structure of the atom.

In the experiment, Rutherford directed a beam of alpha particles (positively charged particles) at a thin sheet of gold foil. He expected the alpha particles to pass straight through the gold foil, or to be slightly deflected due to interactions with the electrons in the gold atoms. However, he observed that some of the alpha particles were deflected at very large angles, and even bounced back in the direction they came from.

This unexpected result led Rutherford to conclude that the atom must contain a very small, dense, positively charged core, which he called the nucleus. Rutherford proposed that most of the mass of the atom was concentrated in the nucleus, and that the electrons orbited around the nucleus at a distance.

The gold foil experiment provided evidence for the nuclear model of the atom, and helped to establish the concept of the atomic number, which is the number of protons in the nucleus and determines the identity of the element. The experiment also provided insight into the size and structure of the nucleus, as well as the forces that hold it together.

## Size of the Nucleus

The size of the nucleus is determined by a number of factors, including the number of protons and neutrons it contains, the energy of the particles within the nucleus, and the forces that hold the nucleus together. The strong nuclear force, which is responsible for holding the nucleus together, has a very short range and becomes weaker over greater distances. This means that the nucleus must be small enough to allow the strong nuclear force to hold the particles together.

The size of the nucleus can also vary depending on the element and isotope of the atom. For example, the nucleus of a hydrogen-1 atom, which contains a single proton, is much smaller than the nucleus of a uranium-238 atom, which contains 92 protons and 146 neutrons.

The size of the nucleus can also be measured experimentally using techniques such as scattering experiments and electron microscopy. These experiments have provided a wealth of information about the structure and properties of nuclei, including their size, shape, and internal structure.

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