P.SCIENCE Lesson 1: NUCLEAR REACTIONS AND ORIGIN OF ELEMENTS

• Nuclear reaction


  A process involving a change to the nuclei of atoms, typically resulting in the transformation of atoms of one element into atoms of another element
• Everything around us is matter, which is composed of varying combinations of any of the 118 elements identified to be present in the universe, including Earth.
• Nuclear Reactions


  Processes in which a nucleus either combines with another nucleus or splits into smaller nuclei

  
• Nuclear Reactions


  • Nuclear Fusion-nucleus combines with another nucleus
  • Nuclear Fission-nucleus splits into smaller nuclei

  
• These processes involve the emission of energetic particles of an atom, a phenomenon known as radioactivity.

  
• Examples of Nuclear Reactions

  • The energy from the Sun - both heat and light energy - originates from a nuclear fusion process that is occurring inside the core of the Sun.
  • Hiroshima and Nagasaki Bombing - An atomic bomb uses either uranium or plutonium and relies on fission, a nuclear reaction in which a nucleus or an atom breaks apart into two pieces.

  
• Most Common Types of Nuclear Reactions

  • Alpha decay: loss of an alpha particle
  • Beta decay: loss of beta particle
  • Gamma radiation: emission of a gamma ray
  • Positron emission: conversion of a proton in a nucleus into a neutron, along with the release of a positron
  • Electron capture: drawing of an electron into an atom's nucleus

  
• Alpha decay


  Loss of an alpha particle
• Beta decay


  Loss of beta particle
• Gamma radiation


  Emission of a gamma ray
• Positron emission


  Conversion of a proton in a nucleus into a neutron, along with the release of a positron

  
• Electron capture


  Drawing of an electron into an atom's nucleus

  
• The existence of all matter is believed to have started with the birth of the universe.
• The big bang theory postulates that approximately 14 billion years ago, a hot, dense mass about one cm in diameter experienced a huge explosion, spreading its products as a fast moving cloud of gas.
• Astronomers believed that a few minutes after the big bang, the universe was composed of approximately 75% hydrogen and 25% helium, and trace amounts of lithium.
• The universe continuously expanded for several years and the cloud of hydrogen and helium gases condensed to form stars, including the sun.
• Over millions of years, the stars made of hydrogen and helium became hotter and denser. During this stellar evolution, nuclear reactions continued, which produced elements heavier than lithium.
• The light elements combined to form atoms of carbon, neon, oxygen, silicon, and iron.
• Cosmic Origin of Elements

  1. Big Bang

  2. Expansion of Universe

  3. Formation of Stars

  4. Stellar Evolution

  5. Production of Heavier Elements