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Universe from Elementary Particles Universe from elementary particles Yes! It all started with a bang!, known as Big-Bang about 13.7 billion years ago. Man has evolved both physically and intellectually over the years to trace back the reason for the bang. This big bang created all the elementary particles and the interaction between them that lead to the formation of the universe as we observe. What makes these elementary particles to be the building blocks of nucleus of an atom? What is the structure and behaviour of nuclei of various elements of matter? To answer these questions we need to study this topic in a detailed manner.

Learning objectives

After completing the topic, the student will be able to:

  • Understand the structure of nucleus and analyze its components, related to all the atoms of the known elements.
  • Determine the size, mass and nuclear density of the nucleus for any given atom depending on the number of its constituents.
  • Discuss and differentiate between the isotopes, isobars and isotones of the atomic elements.
  • Explore the nuclear forces and its characteristic properties that bind the components of the nucleus to build a stable atom.
  • Discuss and relate mass defect to explain the stability of nucleus; also determine the most stable nuclei (of a particular element) among all the elements.
Nuclear energy power station & nuclear medicine imaging Nuclear energy power station & nuclear medicine imaging Nuclear energy is used to produce electricity and also in medicine imaging to identify the defects of a patient(NMR spectroscopy)

The atom is almost all empty space. If we had an atom and wished to see the nucleus, we would have to magnify it until the atom was the size of a large room, and then the nucleus would be a large speck which you could just make out with your eye. The radius of the nucleus is 1,00,000 times smaller than the atom and in terms of volume, atom is a thousand million million times bigger than nucleus.

But nearly all the weight of the atom is in the infinitesimal nucleus. As neutrons and protons in nucleus are very nearly of the same mass as each other and each is about 2000 times as massive as an electron, the total number of protons and neutrons in the nucleus determines all but a small fraction of the mass of an atom.

The energy of the nucleus reveals itself in many ways; nuclear warheads that can destroy cities, submarines driven by nuclear reactors, nuclear power plants and in destroying cancerous cells. Nuclear energy comes from the conversion of mass and can result from nuclear reactions like fission (the splitting of the nucleus) and fusion (the coming together of nuclei).

In case of nuclear fission, nucleus splits into two roughly equal fragments and two or three more neutrons. The sum of these masses is less than that of the original nucleus, and the difference in mass is converted into energy of the motion of fragments which can lead to a nuclear chain reaction in certain conditions. The energy released as a result of nuclear chain reaction is used to run commercial nuclear reactors and generate electricity.

Nuclear medicine is a branch of medicine that uses the nuclear properties of matter in diagnosis and therapy. Nuclear medicine is a safe, painless and cost–effective technique to image the body and treat disease. In diagnosis, radioactive substances are administered to patients and the radiation emitted is measured. In therapy, radio nuclides are administered to treat disease or provide palliative pain relief. Nuclear medicine imaging procedures often identify abnormalities very early in the progress of a disease ‐ long before many medical problems are apparent with other diagnostic tests.

The OPAL detector at CERN The OPAL detector at CERN A technician works on one of two end caps of the OPAL detector at CERN, the European centre for particle physics near Geneva. OPAL is one of 4 giant particle detectors at the LEP collider. LEP collides electrons & positrons accelerated to an energy of 50 GeV in a circular tunnel 100m underground & 27km in circumference. OPAL is a cylindrical assembly of many types of apparatus which fit together like layers of an onion around the point where the particles collide.

Nuclear physics is unfortunately identified with applications of destruction such as submarines driven by powerful nuclear reactors which can travel around the world and sustain a crew for months without surfacing. Nuclear warheads have the power to destroy cities. But, put to right use we can find many important applications for human welfare. Nuclear energy is used to destroy cancerous cells. Nuclei when injected into the body, allow physicians to trace the movement of atoms and make diagnosis. The sunlight that nourishes our planet comes from nuclear reactions inside the Sun.

Nuclear energy can be understood simply as energy that comes from conversion of mass. The nucleus of the atom which is dense and heavy accounts for most of the atom′s weight and almost none of its volume. The nucleus which is responsible for nuclear energy and radioactivity behaves independent of the atom′s electrons which control chemical bonding.

The nuclei of most familiar atoms are stable and do not change, but some of them disintegrate and emit energetic particles that we call radiation. The radiation occurs when some part of the original mass converts to energy. Energy can result from nuclear reactions like splitting of the nucleus (fission) and coming together on nuclei (fusion). In Fission as well as fusion energy comes from conversion of mass into energy.

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