Atomic Structure + Periodic Table

• contained in the nucleus are the protons and neutrons. moving around the nucleus are the electron shells. They are negatively charged.
• proton?


  relative mass = 1

  charge = + 1
• neutron?


  relative mass = 1

  charge = 0
• electron?


  relative mass = very small

  charge = -1
• overall atoms have no charge, they have the same number of protons and electrons. An ion is a charged particle, it doesn't have an equal number of protons to electrtons
• elements are made of atoms with the same atomic number. atoms can be represented as symbols
• isotopes - is an element with the same number of protons but different number of neutrons. same atomic number but different mass number
• compound?

  two or more elements are chemically bonded together.

  e.g. carbon dioxide, magnesium oxide

  are difficult to separate
• equation: to calculate relative atomic weight?


  sum of (isotope abundance x isotope mass number) / sum of abundances of all isotopes
• word equations: left side is the reactants and right side is the products
• mixture?


  2 or more elements that are not chemically bonded together

  easy to separate

  e.g. salt water and air
• chromatography?


  separation of 2 mixtures
• filtration?


  separation of solid and liquid
• evaporation?


  separation of a soluble salt from a solution (quicker method)
• crystallisation?


  separation of a soluble salt from a solution (slower method)
• separation of salt from rock salt?


  1. grind the mixture of rock salt
  2. add water and stir
  3. filter the mixture, leaving the sand in the filter paper
  4. evaporate water from the salt leaving crystals
• distillation?


  separation of mixture of a liquid
• simple distillation?


  separating a liquid from a solution
• fractional distillation?


  separation out a mixture of liquids, like crude oil into fractions (gas 20*c, gasoline , kerosene, diesel oil, fuel oil, lubricating oil, paraffin wax and asphalt)
• metals are found on the left part of the periodic table
• properties of metals?


  strong, malleable, good conductors of electricity and heat. Bond metallically.
• non-metals?


  found on the right of the periodic table
• non-metal properties?


  dull, brittle, not always solid at room temp
• John Dalton?


  start of 19th century - atoms were first described as solid spheres
• JJ Thomson?


  1897 - plum pudding model (the atom is a ball of charge with electrons scattered)
• Ernest Rutherford?


  1909 - alpha scattering experiment ( mass concentrated at the centre, the nucleus is charged. most of the mass is in the nucleus . most atoms are empty space)
• Niels Bohr?


  around 1911 - electrons are in shells orbiting the nucelus
• James Chadwick ?


  around 1940 - discovered that there are neutrons in the nucleus
• electronic structure?


  electrons are found in shells, a maximum of two in the inner most shell, then eight in the 2nd and 3rd shell. the inner shell is filled first.
• group 7 (halogens)?


  non-metals: fluorine, chlorine, bromine and iodine

  As you go down they become less reactive, it is harder to gain an electron because its out shell is further away from the nucleus. The melting and boiling points also become higher.
• group 0 (noble gases)?


  Helium, Neon, Argon, Krypton, Xenon, Radon

  They are very unreactive as they have full outer shells which makes them very stable

  colourless gases at room temperature

  boiling points increase as you go down the group - have greater intermolecular forces because of the increase in the number of electrons
• development of the periodic table?


  early 1800's - elements arranged in atomic weight, the periodic table was not complete because some of the elements had not been found. Some elements were put in the wrong group.

  1869 - Dimitri Mendeleev left gaps in the periodic table, he then put them in order of atomic weight, the gaps show that he believed there was some undiscovered elements. once they were found they fitted in the pattern
• the modern periodic table?

  • elements are in order of atomic weight/ proton number. it shows where the metals and non-metals are.
  • metals are on the left and non metals are on the right.
  • the columns show the groups, the group number shows the number of electrons in the outer shell
  • the rows are the periods - each period shows another full shell of electrons
  • can be used to predict the reactivity
• group 1 (alkali metals) ?

  soft and very reactive

  one electron in the outer shell (very reactive)

  low density

  as you go down the group they become more reactive as they get bigger so it is easier to lose an electron that is further away from the nucleus

  form ionic compounds with non-metals

  react with hydrogen to produce water

  react with oxygen to produce metal oxides

  react with chlorine to produce metal salt