3 ATOMS, ELEMENTS AND COMPOUNDS

3 ATOMS, ELEMENTS AND COMPOUNDS

1. 3.1 Atomic Structure and The Periodic Table

   • All elements are made up of 3 particles
     • Proton
       • Positive charge (1+)
     • Neutron
       • Neutral charge
     • Electron
       • Negative charge (1-)
     • Atomic number [Z] = number of protons (=number of electrons)
     • Mass number [A] = sum of protons and neutrons
   • Isotopes
     • Atoms with different number of neutrons
       • Same amount of protons and electrons
   • Chemical properties depend on electron configuration
     • Noble (inert) gasses [group 8]
       • Non-reactive
       • Full outer shells
     • Alkali Metals [group 1]
       • One electron on outer shell
       • Very reactive
     • Halogens [group 7]
       • Very reactive
       • Seven electrons in outer shell

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