Melting points

• Na to Al :

  • Metals with metallic bonding
  • increasing melting points due to greater positive positive charged ions (Na +1, Mg +2, Al +3)
  • More electrons are released as free electrons, so the attractive electrostatic forces increase from Na to Mg
• Si :

  • Macromolecular i.e., it has a very strong covalent structure.
  • Takes a lot of energy to break , giving a very high melting point.
• P, S, Cl :

  • Simple covalent molecules held with weak van der Waals force.
  • Don't require much energy to overcome so these molecules have relatively low, similar melting points.
• Ar :

  • Noble gas that exists as individual atoms with full outer shell of electrons.
  • Very stable atom and van der Waals forces between them are weak.
  • Very low melting point, exist as gas at room temp.
• Why does Al have a different IE compared to other Period 3 elements?

  • The electron is taken from a new sub shell, in a higher energy level than Mg.
  • It takes less energy to remove.
  • The electron pairing in P orbital means more repulsion
  • Makes it easier to remove.
• Van der Waals force :

  • distance-dependent interaction between atoms or molecules. 
  • caused by correlations in the fluctuating polarizations of nearby particles