periodic table

• add cl2 (aq) to unknown solution and shake. add organic solvent and shake


  Br- : orange aq layer & orange-red organic layer

  I- : brown aq layer & purple organic layer
• reaction with thiosulfate


  cl & br: avg OS of S increases from +2 to +6

  iodine: avg OS of S increase from +2 to +2.5
• reactions with Fe


  Cl2 & Br2: spontaneous reaction with Fe and Fe2+

  I2: spontaneous reaction with Fe only
• why F2 BDE lower than expected

  small atomic size, great repul btwn lp e- on the 2 F atoms, weakening F-F bond
• what is e conductivity dependent on?

  presence and no. of mobile charge carriers
• Si is a metalloid, poor e conductor
• P expands its octet by promoting 1 3s e- to 3d subshell
• S expands its octet by promoting 1 3s e- and 1 3p e- to 3d subshell
• group 2 metals mp

  no clear trend. metals adopt diff crystal structure
• thermal stability

  group 2: charge density

  group 7: H-X bond
• why does H-X bond decrease down grp 17

  • less effective orbital overlap, btwn 1s orbital of H and valence p orbital of halogen.
  • e-neg diff decreases, decrease in bond polarity
• iodine becomes more soluble when KI added


  due to fmtn of soluble (forms ion-dipole int w h2o) complex ion, I3-