atomic structure and periodic table (c1)

• Compound


  Two or more different elements chemically bonded
• Atom


  Smallest part of an element to exist
• Atoms have protons, neutrons, and electrons
• Atomic number is the number of protons
• Mass number is the number of protons and neutrons
• Mixture


  Two or more substances not chemically bonded
• Filtration


  Separate insoluble solids from liquids
• Evaporation


  Heat solution until solvent evaporates
• Crystallisation


  Heat solution in Bunsen burner, stop when crystals form and cool, leave for solution to evaporate
• Simple distillation


  Heat solution, liquid evaporates into vapour, vapour condenses and is collected
• Fractional distillation


  Solution heated, liquid with lowest boiling point evaporates into vapour, passes through fractionating column, condenses back into liquid
• Development of atomic model

  • First thought to be tiny spheres, Thomson's plum pudding model, Rutherford's alpha particle scattering, Bohr's model of electrons orbiting nucleus
• Electrons have a charge of -1, neutrons have no charge, protons have a charge of +1
• Atoms have no overall charge
• Isotopes


  Different forms of the same element that have the same number of protons but a different number of neutrons
• Calculating isotope abundance


  Sum of (isotope abundance + isotope mass) / Sum of abundance of all isotopes
• Periodic table

  • Arranged in increasing atomic (proton) number, periods have increasing number of shells, groups have increasing number of electrons in outer shell
• Development of periodic table

  • Before protons, neutrons and electrons were discovered, elements were ordered by atomic weight,
• Metals


  • Form positive ions, good conductors of heat and electricity, high melting/boiling points, shiny, malleable
• Non-metals


  • Do not form ions or form negative ions, poor conductors, lower densities, low melting/boiling points, dull in colour, brittle
• Group 8 - Noble gases

  • Colourless gases, inert (unreactive), single gases, non-flammable
• Group 1 - Alkali metals


  • One electron in outer shell, soft, low density, low melting point, reactivity increases going down group, form positive ions
• Group 7 - Halogens


  • Non-metals, diatomic molecules, form covalent bonds with other non-metals, form ionic bonds with metals, melting and boiling point increases going down group, reactivity decreases
• Transition metals


  • Hard, strong, good conductors, very dense, high melting points, can form more than one ion, good catalysts, used in medicine, dyes, jewellery, stained glass
• alpha particle experiment
• explain the alpha particle experiment


  -alpha particles fired at a thin sheet of gold

  -some passed through, some defelected, some direction was reversed
• what did the plum pudding model show

  a ball of positive charge with negative electrons embedded in it
• what did mendellev do

  left gaps for undiscovered elements

  predicted unknown elements properties

  changed order based on atomic weight

  grouped elements with similar properties