Module 3 periodic table

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Periodicity- ionisation energy

Periodicity-  regular periodic variation of properties of elements with atomic number and position in the Periodic Table- trend in properties that are repeated across each period

Trends across period- number of protons increases, atmoic radius decreases, attraction between nucleus and outer electrons increases,first ionisation energy increases, electron shielding hardly changes

Trends down a group- number of shells increases, shielding increases, atmoic radius increases, weaker attraction on the outer electrons, first ionisation energy decreases

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Periodicity- boiling points

  • Group 1 to 4 = increase in boiling point
  • Group 4 to 5 = sharp decrease in boiling point 
  • Group 5 to 0 = comparatively low boiling point
  • Giant metallic -> giant covalent -> simple moleculare structures
  • Giant metallic- strong forces between negative delocalised electron and positive ions - metallic bonding
  • Giant covalent- strong forces between atoms - covalent bonding
  • Simple molecular structure- weak forces between molecules - van der waals forces
  • Na to Al- ionic charge increases, ionic size decreases, number of outer electrons increases, attraction increases, melting and poiling points increase
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Group 2

  • reactive, strong reducing agents, oxidise in reaction, lose two electrons
  • reactivity increases down the group
  • decrease in ionisation energy
  • reacts with oxygen vigorously- redox reaction
  • reacts with water to form a hydroxide and hydrogen 
  • solubility increases
  • alkalinity increases
  • ease of thermal decomposition decreases
  • calcium hydroxide- lime to neutralise acid soils
  • magensium hydroxide - milk of magneria to relieve indigestion 
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Group 7

  • low melting and boiling points
  • diatomic
  • boiling point increases down group- increase in electrons- increase in van der waals' 
  • move from gas to solid down the group
  • oxidising agents - remove electrons - gains an electron 
  • oxidising power decreases down the group as reactivity decreases 
  • Cl2- green in water and cyclohexane 
  • Br2 - orange in water and cyclohexane 
  • I2 - brown in water and violet in cyclohexane 
  • Disproportionation reactions:
    -   Cl2 + H2O -> HClO + HCl  (kill bacteria) 
    -   Cl2 + 2NaOH -> NaCl + NaClO + H2O  (bleaching) 
  • simple molecular - weak van der waals' forces 
  • 1/2 X2 + e- -> X-   halogen + electron -> halide ion 
  • chloride - white precipitate, soluble in dilute NH3 
  • bromide - cream preciptate, soluble in conc NH3 
  • iodide - yellow preciptate, insoluble in conc NH3 
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