chemistry c1

• atoms make up all substances and are the smallest part of an element that can exist
• what are compounds?


  Substances formed by the chemical combination of two or more elements.
• how can compounds be separated?

  chemical reactions
• what is a mixture?


  A combination of two or more substances that are not chemically bonded.
• how can mixtures be separated?

  • filtration
  • crystallisation
  • simple distillation
  • fractional distillation
  • chromatography
• the processes of which mixtures are separated are physical processes, so do not involve with chemical reactions and no new substances are made
• what did scientists think atoms were first?

  tiny spheres that could not be divided
• what model was made by the discovery of the electron?

  plum pudding model
• what is the plum pudding model?


  a ball of positive charge with negative electrons embedded in it
• who discovered electrons?

  J.J. Thomson
• how were electrons discovered?

  alpha particle scattering experiment
• what are the steps to the alpha particle experiment?

  1. a beam of alpha particles was aimed at very thin gold foil and their passage through was detected
  2. some of the alpha particles emerged from the foil at different angles, and some even came straight back
  3. the positively charged alpha particles were being repelled and deflected by a small concentration of positive charge in the atom (nucleus)
• what did neil bohr suggest?


  electrons orbit the nucleus at specific distances
• later experiments discover that positive charge of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge (protons)
• what did James Chadwicks work show?


  the existence of neutrons within the nucleus
• what is the relative charge of a proton?

  +1
• what is the relative charge of a neutron?

  0
• what is the relative charge of an electron?

  -1
• number of protons = number of electrons
• what is the overall charge of an atom?

  0
• what is the relative mass of a neutron?

  1
• what is the relative mass of a proton?

  1
• what is the relative mass of an electron?

  very small
• what is the radius of an atom?

  0.1 nm
• what is the relative atom mass?


  an average value that takes account of the abundance of the isotopes of the element
• what is the top number of this element?

  mass number

  
• what is the mass number of an element?


  total number of protons and neutrons
• what does the atomic number of an element show?

  proton number
• what is this number at the bottom?

  atomic number

  
• how many electrons are there in the shell closest to the nucleus?

  2
• how many shells are there in shell 2 of an atom?

  8
• what particles are there in the nucleus of an atom?

  neutrons and protons
• how did john newlands order his periodic table?

  in order of atomic weight
• what did john newlands realise?

  every 8th of the elements in his periodic table had very similar properties. he called this the 'law of octaves' but broke down after calcium
• how did dmitri mendeleev order his table?

  • in order of atomic mass, but not always strictly. in some places he changed the order based on atomic weights.
  • he left gaps for elements he thought were not discovered yet
• elements with similar properties were grouped together in the periodic table