P4

• What is the earliest model of the atom described in the study material?

  Tiny sphere that can't be broken up
• What does the plum pudding model represent?

  A sphere of positive charge with negative electrons stuck in it
• What is the nuclear model of the atom?

  A positively charged nucleus surrounded by a cloud of negative electrons
• In the Bohr model, how do electrons behave?

  Electrons orbit the nucleus at certain distances
• What significant discovery was made about the nucleus?

  The nucleus could be split into smaller particles
• What are the three main components of the current model of the atom?

  Protons, electrons, and neutrons
• What is the charge of a proton?

  +1 charge
• What is the charge of an electron?

  • 1 charge
• What is the charge of a neutron?

  0 charge
• What happens when electrons absorb EM radiation?

  They move to higher energy levels
• What is the significance of the alpha scattering experiment?

  It showed that most of the mass of an atom is concentrated at the nucleus
• What did James Chadwick prove about neutrons?

  Neutrons exist
• How does the nuclear radius compare to the atom's radius?

  The nuclear radius is about 10,000 times smaller than the atom's radius
• What is the overall electric charge of an atom?

  Zero, because the number of electrons equals the number of protons
• What are isotopes?

  Atoms with the same number of protons but different numbers of neutrons
• What is the mass number of an atom?

  The total number of protons and neutrons in an atom
• What is the atomic number of an atom?

  The number of protons in an atom
• What is radioactive decay?

  When an unstable nucleus decays into another element and gives out radiation
• What is ionising radiation?

  Radiation that knocks electrons off atoms, creating positive ions
• What are the three types of nuclear radiation?

  Alpha (α), beta (β), and gamma (γ)
• What does alpha radiation consist of?

  2 neutrons and 2 protons (helium nucleus)
• What does beta radiation consist of?

  A fast-moving electron from the nucleus
• What does gamma radiation consist of?

  Electromagnetic radiation from the nucleus
• What materials can absorb alpha radiation?

  Sheet of paper
• What materials can absorb beta radiation?

  Sheet of aluminium
• What materials can absorb gamma radiation?

  Thick sheets of lead
• What is the range of alpha particles in air?

  Few centimetres
• What is the range of beta particles in air?

  Few metres
• What is the range of gamma radiation in air?

  Longer distances
• What is the ionising power of alpha radiation?

  Strong
• What is the ionising power of beta radiation?

  Moderate
• What is the ionising power of gamma radiation?

  Weak
• What is an example use of alpha radiation?

  Smoke detectors
• What is an example use of beta radiation?

  Material thickness testing
• What is an example use of gamma radiation?

  Medical tracers
• What happens to mass and charge during alpha decay?

  Mass decreases and charge decreases
• What happens to mass and charge during beta decay?

  Mass stays the same and charge increases
• What happens to mass and charge during gamma decay?

  No change in mass or charge
• What is the definition of activity in the context of radioactivity?

  The rate at which a source decays, measured in becquerels (Bq)
• What is the definition of count-rate?

  The number of radiation counts reaching a detector per second