Radioactivity

• What do atoms consist of?

  Nucleus surrounded by electrons
• What charge do protons have?

  Positive charge
• Where are neutrons found?

  In the nucleus
• What charge do electrons have?

  Negative charge
• What does the atomic number (Z) represent?

  Number of protons in an atom
• How does the atomic number determine the element?

  It identifies the specific element
• What is the mass number (A)?

  Sum of protons and neutrons
• What are isotopes?

  Atoms with same protons, different neutrons
• What are radioactive isotopes?

  Unstable isotopes that emit radiation
• What is alpha radiation composed of?

  2 protons and 2 neutrons
• What is the charge of alpha radiation?

  +2 charge
• What is the penetrating power of alpha radiation?

  Low, stopped by paper or skin
• What is the ionizing power of alpha radiation?

  High, can damage cells
• What is beta radiation composed of?

  High-energy electron or positron
• What is the charge of beta minus radiation?

  -1 charge
• What is the penetrating power of beta radiation?

  Medium, stopped by a few mm of aluminum
• What is the speed of beta radiation?

  Fast, close to the speed of light
• What is gamma radiation?

  Electromagnetic wave, high-energy photon
• What is the penetrating power of gamma radiation?

  Very high, reduced by thick lead
• What is the ionizing power of gamma radiation?

  Low, penetrates deeply
• When is gamma radiation emitted?

  After alpha or beta decay
• What is radioactive decay?

  Spontaneous emission of radiation for stability
• What happens during alpha decay?

  Nucleus loses 2 protons and 2 neutrons
• What is the effect on mass number during alpha decay?

  Decreases by 4
• What is the effect on atomic number during alpha decay?

  Decreases by 2
• What happens during beta minus decay?

  A neutron changes into a proton and emits an electron
• What is the effect on mass number during beta minus decay?

  Stays the same
• What is the effect on atomic number during beta minus decay?

  Increases by 1
• What happens during beta plus decay?

  A proton changes into a neutron and emits a positron
• What is the effect on mass number during beta plus decay?

  Stays the same
• What is the effect on atomic number during beta plus decay?

  Decreases by 1
• What happens during gamma decay?

  No change in mass or atomic number
• What is half-life?

  Time for half of nuclei to decay
• Is half-life affected by physical conditions?

  No, it is constant
• How is half-life calculated from activity?

  Using the formula $A =$$A_0 (1/2)^n$
• What does $n$ represent in the half-life formula?


  Number of half-lives that have passed
• How is $n$ calculated?


  $n =$$\frac{t}{T_{1/2}}$
• If a sample’s activity drops from 80 Bq to 10 Bq in 6 hours, what is the half-life?

  2 hours
• What is a Geiger-Müller (GM) tube used for?

  Measures radiation by detecting ionization
• How does photographic film detect radiation?

  Darkens when exposed to radiation