periodicity

• Atomic radius decrease from left to right across a period, because the increased number of protons create more positive charged nucleus and attraction for electrons which are in the same shell with similar shielding
• first ionisation energy is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
• along a period 1st ionisation energy increases as atomic radius decreases and increasing nuclear charge due to the increase in protons which means outer electrons are held more strongly and therefore more energy is required to remove them
• down a group ionisation energy decreases with atoms getting larger so the nuclear attraction between nucleus and outer electrons reduces and increasing amounts of shielding means less energy required to remove outer electron
• Na, Mg and Al

  • they are all metals with metallic bonding with there melting points increasing due to greater positively charged ions so smaller sized ion with a greater positive charge also makes the bonding stronger. (Na + Mg 2+ Al 3+).
  • This also means the more stronger ion the more electrons there are in the outer shell that are released to the sea of electrons
• Si

  Silicon is a macromolecule meaning it contains many strong covalent bonds between atoms so high energy needed to break covalent bonds– very high mp +bp
• Cl2 , P4 , S8

  • Chlorine, phosphorous and sulphur are simple covalent molecules so have weak van der waals between molecules, so low energy is needed to break them – low mp+ bp
  • S8 has a higher mp than P4 because it has more electrons (S8 =128)(P4=60) so has stronger van der waals between molecules
• Ar

  Aragon is monoatomic (existing as an individual atom) so has weak van der waals between atoms
• 1st ionisation energy small drops:

  • Mg + Al = there is a shift between 3s to 3p subshell so Al has one unpaired electron in it's highest energy orbital (3p), and Mg's highest energy orbital (3s) the electrons are paired so breaking up this pair would require more energy

  
  

  • P + S = 3p orbitals are all half filled in phosphorus [3p3] and half-filled orbitals are relatively stable and make ionization difficult

  Sulphur has one more electron [3p4] in the 3p orbitals and is, therefore, more readily ionized than phosphorus due to electron pair repulsion