atomic structure

• What is an atom?

  Smallest part of an element that can exist
• What is an element?


  A substance made up of one type of atom
• How are elements represented?


  Using symbols, in the periodic table
• Approximately how many elements are there?

  100
• What is a compound?

  A substance made up of two or more elements chemically combined in fixed proportions
• How are the elements in a compound separated?

  By chemical reaction
• How are chemical reactions represented?

  By word or symbol equations
• Which group of the periodic table includes sodium and potassium?

  Group 1, alkali metals
• Which group of the periodic table includes chlorine, bromine and iodine?

  Group 7, halogens
• Which group of the periodic table includes helium, neon and argon?

  Group 0, noble gases
• What information does a chemical formula provide?

  Which elements are bonded together, and how many atoms of each are present
• What is a mixture?

  Two or more elements or compounds not chemically bonded together
• Which separation technique is used to separate a mixture of two liquids?

  Distillation
• Which separation technique is used to separate a mixture of more than two liquids?

  Fractional distillation
• Which separation technique is used to separate an insoluble solid and a liquid?

  Filtration
• Which separation technique is used to separate a mixture of coloured substances?

  Chromatography
• Which separation technique is used to separate a soluble solid from its solution?

  Crystallisation
• Before the discovery of the electron what were atoms thought to be?

  Tiny spheres that could not be divided
• What is the 'plum pudding' model of the atom?

  Ball of positive charge with negative electrons embedded in it
• What experiment led to the development of the nuclear model?

  Rutherford's alpha particle scattering experiment
• What happened to the alpha particles fired at thin gold foil in Rutherford's scattering experiment?

  Most alpha particles went straight through, but a few were scattered
• What is the 'nuclear' model of the atom that Rutherford developed that replaced the 'plum pudding' model?

  Mass of the atom is in the centre (nucleus) and the nucleus was positively charged
• Who proposed that electrons orbit the nucleus at specific distances?

  Niels Bohr
• What name was given to the positive particles in the nucleus?

  Protons
• What did James Chadwick discover?

  Neutrons
• In what order were the subatomic particles discovered?

  Electron, proton, neutron
• What is the relative charge on a proton?

  +1 (positive 1)
• What is the relative charge on a neutron?

  0 (no charge)
• What is the relative charge on an electron?

  -1 (negative 1)
• Why are atoms electrically neutral?

  Number of protons = number of electrons
• What name is given to the number of protons in an atom of an element?

  Atomic number
• What does the atomic number (number of protons) determine?

  The element. Atoms of a particular element have the same number of protons
• What is the approximate size of an atom?

  0.1 nm (1 x 10-10 m)
• What is the approximate radius of a nucleus?


  1 x 10-14 m
• Where is almost all the mass of an atom?

  In the nucleus
• What is the relative mass of a proton?

  1
• What is the relative mass of a neutron?

  1
• What is the relative mass of an electron?

  Very small / negligible
• What name is given to the sum of the number of protons and neutrons?

  Mass number
• What are isotopes?


  Atoms of the same element with different numbers of neutrons (same number of protons)