a) Radiation

a) radioactive decay; spontaneous and random nature of decay

bi) α-particles, β-particles, γ-rays; nature, penetration, and range of these radiations

radiation is random and spontaneous

• random

  • the time a nucleus decays is not predictable

  • each nucleus in a sample has the same probability of decay

• spontaneous

  • the probability of decay is not affected by external factors

alpha radiation = two protons + two neutrons

• +2e

• large mass and charge

  • collide with and exert large (electrostatic) forces on surrounding particles

  • highly ionising

  • short range

beta-minus radiation = one electron

• -e

beta-plus radiation = one positron

• +e

• small mass and change

  • collide with and exert small (electrostatic) forces on surrounding particles

  • moderately ionising

  • moderate range

gamma radiation = gamma photons

• no charge

• no mass and change

  • does not collide with and exerts no (electrostatic) forces on surrounding particles

  • lowly ionising

  • long range