C4 B4 P4

C4 B4 P4

1. C4

   • nucleus is made from protons & neutrons
     • atom is neutral, equal protons & neutros
     • elements with the same atomic number but different mass numbers are isotopes
       • elements in the periodic table are arranged in order of increasing atomic number
         • atomic theory - John Dalton
         • outer shell of 8 electrons have a stable structure
           • atoms can be made stable by ionic bonding
           • group - accross
           • period - down
   • water pollutants: nitrate residues (fertilisers), lead compounds (lead pipes), pesticide residues (farming)
   • purifying water: 1. sedementation 2.filtration 3. chlorination