chemistry paper 1

chemistry paper 1

1. ATOM: the smallest part of an element

   • ELEMENT: made up of one type of atom
     • COMPOUND: substance formed when two or more elements chemically bond
       • MIXTURE: two or more substances not chemically bonded
   • atomic structure:
     • number of protons =proton number or atomic number
     • number of protons always=number of electrons
       • number of protons+neutrons=mass
     • electron arrangement
     • extra information need to know
       • • number of protons= number of electrons= atomic number. Number of neutrons = mass number – atomic number
           • Mass number = number of protons + number of neutrons

2. PERIODIC TABLE

   • all the elements we know of
   • Dmitri Mendeleev
     • Arranged the elements in order of increasing atomic mass. The arrangement followed the atomic mass but not the chemical properties
   • . Lothar Meyer
     • Calculated the volume of an atom by dividing the mass with the density of the element.
   • . John Newlands
     • Arranged the elements in order of increasing nucleon number. The chemical properties of every eight elements are similar, and it is known as the law of octaves. The classification was a failure because of: The law of octaves was only accurate for the first 16 elements. There was no position allocated for elements yet to be discovered.
   • ionic bondig
     • noble gases have a full outer shell =are inert (unreactive)
   • how it works
     • 7 rows called periods going across
       • 18 columns called groups going down
         • group
           • group1= alkali metals
             • good conductors of heat and electricity
             • light not very dense
             • have low melting and boiling point compared to other metals
           • group2=alkaline earth metals
             • =2 elements=2 electrons on outer shell
             • group17 or 7=halogens=7 elements=7 electrons on outer shell
               • means that they need to gain 1 electron and become a negative ion tobe stable
               • group 18/8/0=noble gases
                 • full outer shell
                   • density/size and mass of atom and melting point all increase
                 • unreactive because of full outer shell
                 • group 3-12(transition metals) in the centre
                   • physical properties
                     • high density
                     • hard and strong
                     • high melting point
                   • chemical properties
                     • much less reactive than group 1 and 2 metals
                       • many form coloured compounds
                       • can lose more electrons than one on outer shell
       • period
         • show the elements electron shell that is being filled
           • group 1 =1shell, group2=2shells, group3=3shells exct..
           • elements in the same group= similar properties
     • arranged according to atomic number
       • (number of protons in nucleus)

3. topic 2 bonding structure and properties of matter

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