P4- Atomic Structure

• Who theorized that everything was made up of "atoms" in 600 BC?

  Democritus
• What was John Dalton's contribution to atomic theory in 1804?

  He stated that each element was made up of a different type of atom.
• What model did J.J. Thomson create in 1897?

  The plum pudding model
• What did J.J. Thomson discover about electrons?

  He discovered that electrons could be removed from atoms.
• How did the alpha scattering experiment conducted by Rutherford challenge the plum pudding model?

  Particles were detected at greater angles than expected, indicating a small nucleus.
• What were the conclusions drawn from Rutherford's alpha scattering experiment?

  • Most particles went straight through, indicating empty space in the atom.
  • Some particles were repelled at large angles, suggesting a small, positively charged nucleus.
• Who discovered neutrons and completed the development of the nuclear model?

  James Chadwick
• What is the charge of protons?

  Positive
• What are ions?

  Atoms that have gained or lost electrons.
• What are isotopes?

  Atoms with the same number of protons but different numbers of neutrons.
• What are the isotopes of hydrogen mentioned in the material?

  ¹H (Protium), ²H (Deuterium), ³H (Tritium)
• What are the types of radiation and their characteristics?

  • Alpha: Weakly penetrating, absorbed by paper, strongly ionizing.
  • Beta: Moderately penetrating, absorbed by aluminum, moderately ionizing.
  • Gamma: Strongly penetrating, absorbed by thick lead or concrete, weakly ionizing.
• What is the use of alpha radiation in smoke detectors?

  It detects smoke by reducing the number of alpha particles reaching the detector.
• What is radioactive decay?

  It is the process by which an unstable nucleus becomes more stable by emitting ionizing radiation.
• What are the methods for detecting radiation?

  • Cloud chamber
  • Photographic film
  • Geiger-Müller tube
• What are sources of background radiation?

  Cosmic rays, rocks, and radon gas.
• What must be conserved in decay equations?

  Atomic and mass numbers must be the same on each side.
• What happens during alpha decay?

  A nucleus loses 2 protons and 2 neutrons, forming a new element.
• What occurs during beta decay?

  A neutron decays to form a proton and an electron, which is ejected from the nucleus.
• What is gamma decay?

  The composition of the nucleus remains unchanged during gamma decay.
• What is nuclear fission?

  • A neutron collides with a nucleus, causing it to split.
  • Releases energy and produces two daughter nuclei.
  • Can lead to a chain reaction.
• What is the energy released in nuclear fission used for?

  It is used to heat water, which turns turbines to generate electricity.
• What is nuclear fusion?

  • Fuses smaller nuclei to create a larger nucleus.
  • Releases energy.
  • Requires high temperatures (over 100 million °C).
• What are safety precautions when handling radioactive materials?

  Wear gloves, wash hands, and maintain distance while using sources.
• What is the difference between irradiation and contamination?

  Irradiation is exposure to radiation, while contamination is radioactive material on or inside an object.
• What is half-life?

  Half-life is the time taken for half of the radioactive nuclei to decay.
• How is the decay of individual atoms described?

  Decay is random and cannot be predicted for individual atoms.
• What is the significance of background radiation?

  It is the radiation we are always surrounded by.
• What happens to the number of protons during nuclear fission?

  The number of protons remains the same.
• What is the role of neutrons in nuclear fission?

  Neutrons are released to continue the reaction.
• What is the purpose of lead-lined bars in radiation safety?

  They maximize shielding against radiation.
• What is the difference between alpha decay and beta decay?

  Alpha decay involves the loss of protons and neutrons, while beta decay involves the transformation of a neutron into a proton and an electron.
• What is the significance of the half-life of isotopes?

  It indicates the time taken for half of the radioactive nuclei to decay.
• How does the decay of groups of nuclei behave?

  Groups of nuclei usually behave in predictable ways.
• What is the formula for calculating the remaining mass after radioactive decay?

  New mass = original mass - mass lost
• What is the charge of the nucleus?

  Positively charged
• What particles are contained in the nucleus?

  Neutrons and protons
• What is the relative mass of a proton?

  1
• What is the relative charge of a neutron?

  0
• What is the relative mass of an electron?

  0 (0.0005)