Atomic Structure and Periodic Table

• what are all substances made from

  atoms
• what is an atom

  the smallest part of an element that can exist
• what is the radius of an atom

  0.1 nm (nanometers) (1 x 10-10m), is very small
• what is the radius of the nucleus

  1 x 10-14 m (1/10000th of the radius of an atom)
• where is most of the mass in an atom located

  in the nucleus
• what can elements be represented as

  symbols
• how many elements are there

  about 100
• where are elements shown

  periodic table
• what is a compound

  two or more different atoms chemically joined together in fixed proportions
• how can compounds be separated into their elements

  by chemical reactions
• are the properties of a compound the same as the elements they are made from

  no
• what is a mixture

  two or more elements or compounds not chemically bonded together, the chemical properties of each substance in the mixture are unchanged
• 5 ways to separate a mixture

  filtration, crystallisation, simple distillation, fractional distillation and chromatography
• why are the techniques used to separate mixture described as physical processes

  as mixtures contain two or more elements or compounds not chemically combined
• how does filtration work

  • pass through filter paper
  • liquid passes through
  • insoluble particles get caught by the filter paper
• how do you carry out crystalliastion

  evaporation dish and heat source. Filter crystals out of the solution
• how can you get sand and salt from a mixture of the two

  • dissolve in water
  • salt is soluble, sand isn't.
  • Filter to remove sand
  • then use crystallisation
• what two processes are involved in distillation

  evaporation and condensation
• where is the hotest part in fractional distillation

  the bottom
• what property must the mixture have to be able to separate by fractional distillatiom

  each part of the mixture must have different boiling points
• what is an element

  a substance made up of only one type of atom
• what is a molecule

  two or more atoms joined together
• where are the reactants found in an equation

  left hand side
• where are the products found in an equation

  right hand side
• what is distillation

  the separating of a liquid using evaporation and then condensation
• a method used to separate two or more liquids

  fractional distillation
• a method used to separate the coloured compounds in a mixture

  chromatography
• a method used to separate an insoluble solid from a liquid

  filtration
• what is crystallisation

  a way to separate a dissolved solid from a solution by evaporation to leave crystals of the solid
• what sub atomic particle was discovered first

  electron
• before electrons where discovered, was it thought that atoms could be divided

  no
• before electrons were discovered, atoms were thought to be what

  tiny spheres
• what model did the discovery of the electron lead to

  plum pudding model
• what was the plum pudding model

  that the atom was a ball of positive charge with negative electrons embedded in it
• what model replaced the plum pudding model

  Nuclear model
• what experiment led to idea that mass of the atom was concentrated in the centre

  alpha scattering experiment
• what would happen with the alpha particle experiment if the plum pudding model was correct

  expect particles to pass straight through or slightly deflected
• what was observed in the alpha scattering experiment

  alpha particles where fired at a thin sheet of gold. Most of the particle passed through with some deflected more than expected and some deflected backwards
• what model replaced the plum pudding model

  nuclear model, have a positively charged nucleus where most of the mass is concentrated and most of the atom is empty space
• who led to the idea that electrons are in orbitals/shells

  Niels Bohr