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Atoms, Ions and Compounds

OCR AS-level ChemistryTopic 1 of 1017 lessons

Revision notes for Atoms, Ions and Compounds in OCR Chemistry A (H032). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.

  1. The Nuclear Atom.An atom consists of a nucleus which contains two types of subatomic particles - protons and neutrons.
  2. Atomic NumberThe atomic number is the number of protons in the nucleus.
  3. IsotopesIsotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
  4. IonsA positively or negatively charged atom is called an ion.
  5. Carbon-12Carbon-12 is used as the standard isotope on which to base all the masses of atoms.
  6. Relative Isotopic Mass: Relative isotopic mass is the mass of an isotope of an atom compared to 1/12th the mass of a carbon-12 atom.
  7. Relative Atomic MassBecause most elements have more than one isotope and naturally occurring elements have different proportions of each isotope, the relative atomic…
  8. The Mass SpectrometerA mass spectrometer can be used to experimentally measure the percentage abundances of isotopes in a sample of an element.
  9. Calculating Relative Atomic MassNeon has two isotopes.
  10. Chemical FormulaeAn ionic compound contains cations (positive ions) and anions (negative ions).
  11. Polyatomic ionsSimple ions are formed from the loss or gain of electrons from single atoms.
  12. Chemical EquationsChemical equations are used to represent chemical reactions.
  13. Electron ShellsAn electron can be considered to be a cloud of negative charge.
  14. SpinThe Pauli exclusion principle states that two electrons can occupy the same orbital as long as they have opposite spin.
  15. Ionisation EnergyThe First Ionisation Energy is the energy needed to remove one electron from each atom of one mole of atoms in their gaseous state to form one mole…
  16. Successive Ionisation EnergiesThe first ionisation energy is the least endothermic as energy is needed to remove an electron from a neutral atom.
  17. Trends in Ionisation EnergyIonisation energies increase across a period.

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