Atomic Structure

• Who replaced the Plum Pudding Model with the Nuclear Model?

  Rutherford
• What did Rutherford's alpha scattering experiment demonstrate?

  Atoms have a concentrated nucleus
• How did the results of the alpha scattering experiment contradict the Plum Pudding Model?

  Some alpha particles were deflected back
• What charge does the nucleus of an atom have?

  Positive charge
• What surrounds the nucleus in the nuclear model of the atom?

  A cloud of electrons
• What did Niels Bohr propose about electron orbits?

  Electrons orbit at specific energy levels
• What are the two types of particles that make up the nucleus?

  Protons and neutrons
• What is the mass number of an atom?

  Sum of protons and neutrons
• What defines isotopes of an element?

  Same number of protons, different neutrons
• What happens to unstable isotopes over time?

  They decay into other elements
• What is the process called when unstable isotopes decay?

  Radioactive decay
• What types of radiation do radioactive substances emit?

  Alpha, beta, and gamma radiation
• What is ionising radiation?

  Radiation that knocks electrons off atoms
• What is an alpha particle composed of?

  Two protons and two neutrons
• How far can alpha particles travel in air?

  A few centimeters
• What stops alpha particles?

  A sheet of paper
• What is a beta particle?

  A fast-moving electron
• How do beta particles interact with materials?

  They penetrate moderately far
• What is the charge of a beta particle?

  -1
• What happens to a neutron when a beta particle is emitted?

  It turns into a proton
• What are gamma rays?

  Waves of electromagnetic radiation
• How do gamma rays interact with materials?

  They penetrate far without being stopped
• What materials can absorb gamma rays?

  Thick sheets of lead or concrete
• What are the key characteristics of alpha, beta, and gamma radiation?

  • Alpha:
  • Helium nuclei, strongly ionising, stopped by paper
  • Beta:
  • Fast-moving electrons, moderately ionising, stopped by aluminum
  • Gamma:
  • EM waves, weakly ionising, stopped by lead or concrete
• Why is alpha radiation unsuitable for sterilising medical equipment?

  It cannot penetrate packaging effectively
• What happens to the charge and mass of the nucleus during alpha decay?

  Charge decreases, mass decreases
• What particle is emitted during alpha decay?

  Helium nucleus
• What is the effect of beta decay on the nucleus?

  Increases the charge by one proton
• What happens to a neutron during beta decay?

  It transforms into a proton and electron
• What is the notation for a beta particle in nuclear equations?


  e
• What is the nuclear equation for beta decay of Carbon-14?

  Carbon-14 → Nitrogen-14 + e
• What do gamma rays do to the nucleus?

  They do not change charge or mass
• What is the definition of half-life?

  Time for radiation to halve
• How is radioactivity measured?

  Using a Geiger-Müller tube and counter
• Why is radioactive decay considered random?

  You can't predict which nucleus will decay
• How can half-life be used in practice?

  To predict radiation emission over time
• What is the difference between irradiation and contamination?

  Irradiation is exposure, contamination is particles
• What makes contamination particularly dangerous?

  Radioactive particles can decay and harm
• Why are alpha sources considered the most dangerous?

  They cause localized damage in the body
• How does beta radiation affect the body compared to alpha radiation?

  Beta radiation is less damaging inside the body