Chemistry 1.1

Chemistry 1.1

1. Atoms

   • All substances made from atoms
     • Substance only 1 sort of atom = element
       • Elements shown in Periodic table
   • Small central nucleus
     • Made of Protons & Neutrons
       • Surrounded by Electrons
         • Electrons fill shells/ energy levels
           • Always fill lowest shell
             • Structure (2, 8, 8)
         • Metals = loose electrons & form positive ions
         • Non Metals = gain electrons & form negative ions
       • Same element same no. protons
       • Diff element diff no. protons
     • Charges
       • Proton = +1
       • Neutron = 0
       • Electron = -1
       • No. Protons = No. Electrons
         • Atoms no overall charge

2. Periodic Table

   • Atom each element = chem symbol
   • Atomic no. = proton no.
   • Mass no. = sum protons & neutrons
   • Group = Down
     • Same Group = Same no. outer electrons
       • Similar chem. properties
       • Group 0 = Nobel Gases
         • Noble gases 8 outer electrons (exc. Helium which has 2)
         • Unreactive
           • Full outer shells
   • Period = Across

3. Chemical reactions

   • During reaction atoms bond & form compounds
     • Involves giving, taking / sharing electrons
     • Compounds formed from metals & non metals = consist ions
     • Compounds formed non metals consist atoms
       • Covalent bonds
   • Represented by word/ symbol equations
   • No atoms made/ lost : Mass = same