C1: atomic structure

• What is the basic concept of Dalton's model of the atom?

  The atom is a solid sphere that cannot be divided into smaller parts.
• What did Dalton's model not include?

  Protons, neutrons, or electrons.
• What were the first sub-atomic particles discovered?

  Electrons.
• What does the plum pudding model of the atom describe?

  A cloud of positive charge with negative electrons embedded in it.
• What experiment led to the discovery of the nucleus?

  The alpha scattering experiment.
• What were the steps of the alpha scattering experiment?

  1. Alpha particles were fired at gold foil.
  2. Expectation: particles would pass straight through.
  3. Observation: some particles bounced back and were deflected.
  4. Conclusion: positive charge is concentrated in a small space called the nucleus.
• What did scientists suggest about the nucleus after the alpha scattering experiment?

  The positive charge must be concentrated in a small space at the center.
• What model replaced the plum pudding model?

  The nuclear model.
• In the nuclear model, how do electrons behave?

  Electrons orbit the nucleus but not at set distances.
• What did Niels Bohr contribute to the atomic model?

  Electrons must orbit the nucleus at fixed distances called shells or energy levels.
• What is the charge of a proton?

  +1.
• What particle did James Chadwick discover?

  The neutron.
• How much smaller are atomic nuclei compared to atoms?

  About 10,000 times smaller.
• What is the charge of an electron?

  • 1.
• Where are protons and neutrons located in an atom?

  In the nucleus.
• What is the approximate radius of an atom?

  100 pm.
• What is the arrangement of electrons in an atom?

  • Up to 2 electrons in the first shell.
  • Up to 8 electrons in the second shell.
  • Up to 8 electrons in the third shell.
  • Shells must be filled completely before moving to the next.
• What are isotopes?

  Atoms of the same element with different numbers of neutrons.
• What does relative atomic mass represent?

  An average of all the isotopes of an element.
• How is relative mass defined for protons, neutrons, and electrons?

  Protons and neutrons have a relative mass of 1, while electrons are considered 0.
• What are the characteristics of mixtures?

  • Composed of two or more elements or compounds.
  • Substances are not chemically bonded.
  • Properties of the substances are retained.
• How can mixtures be separated?

  Using physical processes that do not involve chemical reactions.
• What are the methods for separating mixtures?

  1. Filtration - insoluble solids from a liquid.
  2. Crystallization - soluble solid from a solution.
  3. Simple distillation - solvent from a solution.
  4. Fractional distillation - two liquids with similar boiling points.
  5. Paper chromatography - identify substances in a mixture.
• What are key terms related to atoms and particles?

  • Abundance
  • Atom
  • Atomic number
  • Compound
  • Electron
  • Element
  • Energy level
  • Isotope
  • Neutron
  • Nucleus
  • Orbit
  • Relative atomic mass
  • Relative charge
  • Relative mass
  • Proton
  • Shell