periodicity of group 3

• as you go across the period, the atomic radius decreases as there higher nuclear charge, due to more protons attracting the electrons, as the shell number stays the same
• first ionisation energy generally increases across the period,

  exceptions are group 2 and group 3 , group 5 and group 6
• Na, Mg, Al are metals , they form metallic bonds
• Si - metalloid, forms a giant covalent lattice
• P,S,Cl - non-metal and form simple covalent bonds
• melting points of the metals in period three increase

  1. the charge of the cations increase
  2. so there are more delocalised electrons which produce stronger metallic bonds as there is stronger attraction between delocalised electrons and cations
  3. more energy required to overcome the strong metallic bonds
• macromolecule is a large molecule - Si is an example
• 4 phosphorus atoms bond

  8 sulfur atoms bond

  2 chlorine atoms bond
• Si has strong covalent bonds so has a really high melting point (higher than Al)
• P S and Cl melting points depends on their vanderwaal forces , S8 has the stronger VDWf , then P4 then CL2
• argon has the lowest melting point