CHEMISTRY 1.3

CHEMISTRY 1.3

1. Electron arrangement in atoms

   • Electrons arranged in shells around nucleus
     • Each shell represents different energy level
       • Lowest energy level=Closest to nucleus

2. Electron shell diagrams

   • Draw diagrams, show electron arrangement in atom
   • Energy level (shell), hold certain electron number
     • First, lowest energy level holds 2 electrons
       • Second energy level holds 8 electrons
         • Third energy level hold 8 electrons, fourth begin, fill up & so on
   • Can not draw atoms, write electron number, each energy level
     • Electronic structure

3. Electrons & periodic table

   • Atoms, main groups, same electron in highest energy level
     • Electrons (outer electrons), outermost shell
       • All elements, group 1, one electron (highest energy level)

4. Properties, group 1 elements

   • Lithium, sodium, potassium
     • Alkali metals
   • Chemical properties, element, depend, electron number
     • Element reacts, determined, electron number (highest energy level or outermost shell)
       • Elements, same group, same electron number (highest energy level), all react similar way
   • Elements in group 0, noble gases (unreactive)
     • Atoms, stable electron arrangement
       • 8 electrons except helium (2 electrons)

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