Topic 4 - Atomic Structure

• What is the focus of nuclear physics?

  It studies atomic nuclei.
• Who discovered that atoms are made of charges?

  JJ Thompson
• What model did JJ Thompson propose for the atom?

  Plum pudding model
• What did Ernest Rutherford discover about the atom?

  The positive part is very concentrated and heavy.
• What is the nucleus of an atom?

  The center containing protons and neutrons.
• Who discovered that electrons exist in shells?

  Neil's Bohr
• What are the two types of charges in an atom?

  Protons and neutrons
• What are isotopes?

  Atoms of the same element with different neutrons.
• What does the atomic number represent?

  The number of protons in the nucleus.
• What does the mass number indicate?

  Protons plus neutrons in the nucleus.
• How many neutrons does a carbon atom with mass number 12 have?

  6 neutrons
• What is gamma radiation emitted by?

  The nucleus of an atom.
• What is the danger of gamma radiation?

  It can ionize atoms and cause cancer.
• What type of decay do heavier nuclei like americium-241 undergo?

  Alpha decay
• What is an alpha particle composed of?

  Two protons and two neutrons.
• How does the nuclear decay equation represent alpha decay?

  It shows the nucleus decaying into parts.
• What is the atomic number of an alpha particle?

  2
• What is the mass of an alpha particle?

  4
• What happens during beta decay?

  A neutron turns into a proton and electron.
• What is the charge of a beta particle?

  -1
• How does beta radiation compare to alpha radiation?

  Beta is less ionizing but more penetrating.
• What material can stop beta radiation?

  A few millimeters of aluminum.
• What is the purpose of a GM tube?

  To detect radiation emitted from sources.
• What is background radiation?

  Radiation from natural and man-made sources.
• How do you calculate corrected radiation count?

  Subtract background count from total count.
• What is the use of alpha radiation in smoke detectors?

  It detects smoke by ionizing air particles.
• Why is gamma radiation dangerous despite low ionizing ability?

  It can penetrate and reach living tissues.
• What materials can reduce gamma radiation intensity?

  Lead and concrete.
• What is radioactivity?

  The rate of decay of radioactive sources.
• How is radioactivity measured?

  By radiation count divided by time.
• What is half-life?

  The time for activity to decrease by half.
• How do you find the half-life from a graph?

  Half the initial number and measure time.
• How does the half-life remain constant?

  It takes the same time regardless of amount.
• If a sample starts at 96 Bq and falls to 12 Bq, how many half-lives occurred?

  Three half-lives
• What is the half-life if 12 months equals three half-lives?

  4 months
• What happens during nuclear fission?

  A nucleus splits into two daughter nuclei.
• What is released during nuclear fission?

  Energy and additional neutrons.
• What is a chain reaction in nuclear fission?

  Neutrons cause further fission in nuclei.
• What is the difference between fission and fusion?

  Fission splits nuclei, fusion combines them.
• What happens in the Sun during fusion?

  Light nuclei combine to form heavier nuclei.