BRAINCAKEShapes and Intermolecular Forces
Revision notes for Shapes and Intermolecular Forces in OCR Chemistry A (H032). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Electron Pair Repulsion TheoryThe electron pair repulsion theory can be used to predict the shape and bond angles of covalent molecules and polyatomic ions.
- Three and Four Electron PairsBoron and aluminium have six electrons in the outermost shell in BF3 and AlCl3.
- BF3 and SF6 and PCl5Boron trifluoride has three bonding pairs and has a trigonal planar shape.
- Polyatomic ions.The carbonate CO32- and nitrate ions NO3- are trigonal planar as they both have three bonding regions of electron density surrounding the central…
- More examples.One bonding pair (linear): carbon monoxide C≡O HF cyanide ion C≡N- oxygen O=O Two bonding pairs (linear): BeI2 carbon dioxide O=C=O carbon disulfide…
- ElectronegativityElectronegativity is the attraction of a bonded atom for the pair of electrons in a covalent bond.
- Bond PolarityIn a non-polar bond, the bonded electron pair is shared equally between the two bonded atoms because either the atoms have the same or similar…
- Polar Solvents and SolubilityPolar molecules and ionic substances dissolve in polar solvents such as water because the molecules of the polar solvent attract the ions or…
- Induced Dipole-Dipole Interactions (London Forces)Intermolecular forces are weak interactions between the dipoles of molecules.
- Permanent dipole-dipole interactionsIf you compare fluorine molecules F-F with H-Cl molecules, the molecules have the same shape and number of electrons.
- Solubility of Simple MoleculesPolar covalent molecules may dissolve in polar solvents.
- Hydrogen BondsHydrogen bonds are permanent dipole-dipole interactions between the hydrogen in a H-F, H-N or H-O bond and an electronegative atom containing a lone…
- Boiling Points of Hydrides and Intermolecular forcesThe boiling points of hydrides generally increase across a period from groups 4 to 7.