CHEMISTRY 1.2

CHEMISTRY 1.2

1. Atomic structure

   • Nucleus contains 2 types particles (proton, neutron)
     • Third particle (electron) orbits nucleus
   • Electron number=Proton number
   • Protons (positive charge)
     • Neutrons (no charge), neutral
       • Nucleus overall positive charge
   • Electrons (negative charge)
     • Relative charge
       • Proton (+1)
       • Electron (-1)
   • Atom, equal protons & electrons, (positive & negative charge cancel out)
     • No overall of atom (charge 0)
   • Charge
     • Protons, positive
     • Neutrons, neutral
     • Electrons, negative

2. Atomic number & periodic table

   • All atoms, particular element, same proton number
     • Proton number=Atomic number
   • Elements in periodic table arranged, order, atomic number (proton number)
     • Atomic number 8, identify using periodic table, 8th element listed
   • Read periodic table left to right, top to bottom

3. Mass number

   • Proton + neutron number in nucleus, atom, mass number
     • Atom, 5 protons, 4 neutrons, mass number=9 (4+5=9)
   • Given atomic number & mass number, workout proton, neutron & electron number
     • Argon, atomic number 18, mass number 40
       • Atomic number 18=18 protons
         • 18 elctrons (Protons=Electrons)
           • Mass number 40, so, 22 neutron (40-18=22)
             • Neutrons number=Mass number - atomic number

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