Periodicity

• arrangement?


  by proton number, bottom number.
• groups & period?


  groups (columns) & periods (rows)- periods- same number of electron shells. groups same number of outer electrons.
• atomic radius?


  decreases across period- more protons so electrons more attracted.
• melting point?


  Metallic bonding- (Na, Mg, Al) b.p decreases, more delocalised electrons so attraction stronger.
• Structure?


  Phosphorus and Silicon + Cl2 - VDW weak IMF. sulfur the biggest molecule so more VDW.