7.2. Radioactivity

• What is the definition of radioactivity?

  Unstable nuclei emitting radiation
• What is the origin of natural radioactivity?

  Spontaneous decay of unstable nuclei
• What type of particle is emitted during alpha decay?

  Helium nucleus
• Gamma decay changes the atomic or mass number of a nucleus.

  False
• What happens to the atomic number during beta decay with electron emission?

  Increases by 1
• Beta particles can increase or decrease the atomic number by 1
• In alpha decay, the atomic number decreases by 2.


  True
• Match the decay type with its effect on the atomic number:

  Alpha ↔️ -2

  Beta ↔️ ±1

  Gamma ↔️ 0
• Match the decay type with its effect on atomic and mass numbers:

  Alpha ↔️ Atomic: -2, Mass: -4

  Beta ↔️ Atomic: ±1, Mass: 0

  Gamma ↔️ Atomic: 0, Mass: 0
• Beta particles have moderate penetrating power and can be stopped by a thin sheet of aluminum
• What is a nuclear equation used to represent?

  Radioactive decay process
• What happens to the atomic and mass numbers during alpha decay?

  Atomic: -2, Mass: -4
• What is half-life defined as in radioactive decay?

  Time for activity to halve
• The decay constant is inversely related to the half-life.


  True
• Artificial radioactivity involves the spontaneous decay of unstable nuclei.

  False
• Artificial radioactivity is induced by bombarding stable nuclei with particles.

  True
• What are the three primary types of radioactive decay?

  Alpha, beta, gamma
• What type of radiation is emitted during gamma decay?

  Electromagnetic radiation
• Gamma rays require thick lead or concrete shielding due to their high penetrating power.


  True
• Match the decay type with its change in atomic and mass numbers:

  Alpha ↔️ Z - 2, A - 4

  Beta ↔️ Z ± 1, A - 0

  Gamma ↔️ Z - 0, A - 0
• Radioactive activity decreases over time following an exponential decay model.
• The decay constant \lambda</latex> is related to the half-life by $\lambda =$$\frac{\ln 2}{t_{1 / 2}}$ where <tex>$t_{1 / 2}$</tex> is the half-life.
• What is half-life defined as?

  Time for activity to halve
• What does $A$ represent in the exponential decay equation?


  Activity at time $t$
• What is one medical application of radioactivity using radioactive tracers?

  Diagnostic imaging
• Radioactivity has no applications outside of scientific research.

  False
• Natural radioactivity occurs spontaneously in elements like uranium
• Artificial radioactivity produces synthetically created isotopes
• Alpha decay reduces the mass number by 4
• Arrange the following steps in alpha decay in the correct sequence:

  1️⃣ Unstable nucleus emits a helium nucleus

  2️⃣ Atomic number decreases by 2

  3️⃣ Mass number decreases by 4
• Match the decay type with its emitted particle:

  Alpha ↔️ Helium nucleus

  Beta ↔️ Electron or positron

  Gamma ↔️ Electromagnetic radiation
• What is the emitted particle in alpha decay called?

  Helium nucleus
• Beta decay involves the emission of an electron or a positron
• Alpha particles have high penetrating power.

  False
• Gamma decay changes the atomic or mass number of the nucleus.

  False
• What are the two key properties that distinguish alpha, beta, and gamma radiation?

  Penetrating power and ionizing ability
• What type of shielding is required to stop gamma rays?

  Thick lead or concrete
• A nuclear equation must be balanced to conserve both atomic and mass number.


  True
• Match the decay type with its effect on atomic and mass numbers:

  Alpha ↔️ Atomic: -2, Mass: -4

  Beta ↔️ Atomic: ±1, Mass: 0

  Gamma ↔️ Atomic: 0, Mass: 0
• The decrease in radioactive activity over time follows an exponential decay model