atomic structure & the periodic table

• define atomic number

  no of protons
• define atomic mass

  no of protons + no. of neutrons
• give the ways to separate mixtures

  fractional distillation - two liquids w similar boiling points

  crystallisation - soluble solid from a solution

  simple distillation - solvent from a solution

  filtration - insoluble solids and liquids

  paper chromatography - identify substances from a mixture in solution
• how do you find relative atomic mass of an element?


  abundance of isotope 1 x mass of isotope 1 + abundance of isotope 2 x mass of isotope 2 / 100
• define molecule


  a group of atoms bonded together
• define relative atomic mass?

  avg mass of all atoms in an element
• electronic structure?

  2,8,8
• order of developments in the atom (people)?

  Dalton

  JJ Thomspon

  Rutherford

  Bohr

  Chadwick
• order of structure of atom?

  atom as a solid sphere (Dalton) -> plum pudding model (Thompson) -> Rutherford's alpha particle -> Bohr electron shells -> Chadwick and neutrons
• what was expected during the gold foil experiment?


  particles to pass straight through the sheet
• what happened during the gold foil experiment?


  some particles were repelled, some passed through and some were absobed
• what did the results of the gold foil experiment imply?


  that there must be negative and positive subatomic structures
• what is the radius of an atom?


  1 x 10^-10
• what is the radius of a nucleus?


  1 x 10^-14
• how were elements arranged in the early periodic table?


  increasing atomic weight
• how did Mendeleev arrange elements?


  by similar chemical properties, increasing atomic mass, and leaving gaps for undiscovered elements
• what are the properties of metals?

  malleable

  shiny & sonorous

  high melting/boiling points
• why do metals have high melting/boiling points?


  lots of energy needed to overcome the strong metallic bonds
• what type of ions do metals form?


  positve
• what are the properties of non-metals?


  brittle

  dull in colour

  low density

  low melting/boiling points
• what type of ions do non-metals form?


  negative
• what are the features of transition metals?

  have no group number

  are colourful

  good catalysts

  can form more than 1 ion
• what are the features of alkali metals?


  soft

  have a low density

  low melting points

  extremely reactive
• how does reactivity change in group 1?


  reactivity increases going down the group

  • electrons are farther away from the nucleus making it easy for them to be lost
• how do melting/boiling points change in group 1?


  decrease going down the group
• what type of compounds do alkalis form with non-metals?


  ionic compounds
• what are group 7 elements called?

  halogens
• how are group 7 elements found in nature?


  as diatomic molecules that form covalent bonds
• what type of bonds do halogens form with other non-metals?


  covalent bonds
• how does reactivity change going down group 7?


  reactivity decreases going down
• why does reactivity decrease going down group 7? (4)


  outermost shell is farther away from the nucleus therefore electrostatic forces of attraction needed to gain an electron decreases, making it harder to react easily
• when forming ionic bonds with metals the halogens form halide ions
• in displacement reactions, more reactive halogens displace less reactive halogens
• noble gases are inert, non-flammable, and very unreactive
• how does boiling point change in noble gases?


  increases going down
• what state are noble gases at room temp?


  gases
• what are the properties of mixtures?


  can be separated by physical techniques

  a combination of elements or compounds

  no chemical bonds

  properties of mixtures = properties of its compounds
• what are mixtures?


  2 or more elements not substances bonded together
• what are compounds?


  2 or more substances chemically bonded together
• what methods can you use to separate soluble solids from solutions?

  evaporation

  crystalisation