Atoms and Elements

Atoms and Elements

1. Atomic structure

   • nucleus
     • protons
       • positive
       • mass of one
     • neutrons
       • neutral
       • mass of one
     • positive
   • electron shells
     • 2, 8 ,8
     • electrons
       • negative
       • almost 0

2. elements

   • one type of atoms
   • atomic mass
     • neutrons and protons
   • atomic number
     • neutrons
   • Capital then lower case
     • Eg. He

3. Compounds

   • two or more types of elements joined together
   • easily seperated

4. Mixtures

   • mix of different elements and compounds
   • easily seperated

5. Reactivity and the periodic table

   • groups all have same no. of electrons in outer shell
   • all atoms want a full outer shell
   • alkaline metals
     • 1 electron in outer shell
       • lose it
     • more reactive further down
       • less attraction to nucleus the further out they are
   • halogens
     • 7 electrons in outer shell
       • react with alkalines
     • less reactive further down
       • more attraction to nucleus if less shells
         • can gain electrons easier further up
   • noble gases
     • full outer shell, not reactive

6. materials

   • metals
     • conductors
       • electricity
       • heat
     • ductile
       • made into wires
     • malleable
       • can be hammered into sheets
   • others
     • insulators