Atomic Structure and the Periodic Table (Paper 1)

Atomic Structure and the Periodic Table (Paper 1)

1. Atoms, Elements, Compounds and Mixtures

   • Atoms, Elements and Compounds
     • Element=a substance that contains only one type of atom
       • Atom= smallest part of an element
     • Compound=atoms of two or more elements tht are chemically combinded
       • can be broken into seperate components by electrolysis or chemical reactions
   • Equations
     • Reactants= substances that react together
       • Products=new substance that is formed by the reaction of the reactants
     • total mass of reactants=total mass of products formed
       • no atoms can be created or destroyed
   • Separating Mixtures
     • Mixtures= consist of two or more elements NOT chemically combinded
     • Filtration= separates soluble solids from insoluble solids
       • EG: salt and sand
     • Crystallisation=obtain a soluble solid from a solution
       • EG:salt crystals from salty water
     • Simple Distillation= obtains a solvent from a solution
     • Fraction Distillation= separates mixtures when the components have different boiling points
       • EG: oxygen and nitrogen as they have different boiling points
         • so evaporate at different times
     • Chromatography=separates coloured components of a mixture
       • EG: ink in a pen

2. Atoms and the Periodic Table

   • Scientific Models of the Atom
     • Plum Pudding Model
       • JJ Thomson discovered electrons in 1898
       • "A sea of positive charge with embedded negative elecrons"
     • Nuclear Model
       • Rutherford examined the results from the alpha particle scattering
         • said that the concentrated charge was called the Nucleus
       • Bohr deducted that electrons must orbit the nucleus at specific distances
       • Chadwick provided evidence that neutrons are within the nucleus
     • Alpha Particle Scattering
       • Alpha particles were fired at a sheet of gold
         • some particles went straight through meaning empty space
         • some particles were reflected back which showed a concentrated charge
       • carried out by Marsden and Geiger
   • Subatomic Particles
     • Proton
       • Relative Mass= 1
       • Charge= +1
     • Neutron
       • Relative Mass=1
       • Charge= 0
     • Electron
       • Relative Mass= very small
       • Charge= -1
   • Isotopes and Electron Configuration
     • Isotope= same number of protons but differentnumber of neutrons
     • first shell holds 2 electrons
     • any other shells hold up to 8 electrons
     • Electron Configuration= shows how electrons are arranged around the nucleus in shells

3. The Periodic Table

   • Development of the Periodic Table
     • Newlands
       • tried to put together the first periodic table in 1864
         • were only 63 elements and many were undiscovered
         • ordered the known elements in atomic weight and missing elements caused problems
     • Mendeleev
       • realised elements were in wrong place and some missing
       • made his periodic table in 1869 and left gaps for missing elements to allow for discovery
         • used his periodic table to predict the missing elements
         • ordered the elements in increasing order of atomic number (number or protons)
   • Group 0
     • also known as noble gases
     • full outer shells
     • very stable
     • boiling points increase as you go down the group
   • Group 1
     • also known as alkali metals
     • one electron in their outermost shell
     • more reactive as you go down the group
       • due to the electron being further away from the nucleus
     • have low boiling points which decrease as you go down the group
     • low density
   • Group 7
     • also known as halogens
     • seven electrons in the outermost shell
     • reactivity decreases as you go down the group
     • going downthe group increrases boiling points
   • Transition Metals
     • centre of periodic table
     • form coloured compounds
     • can be used as catalysts