3. Chemical bonding

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6 thoughts on “3. Chemical bonding

  1. I don’t really understand the relationship between bond length and bond strength especially the case when noble gases don’t have bond length so we have to use their radius or something…


    • And bond length increases, bond strength decreases.

      A covalent bond comes about when two nuclei are attracted to the same set of electrons. A bond is a force of attraction. The distance between the two nuclei is the bond length (sometimes called the ‘internuclear distance’). When one or more of the attracting nuclei get further from the e-, and hence from each other, then the attraction, i.e. bond strength, lowers.

      Noble gases are terrible at making bonds because the attraction for e- by their nucleus is so weak. (note they can still form bonds but they are not very stable) e.g. XeF6. The bond, or attraction, is so weak because they have many completely full inner shells, hence a lot of shielding of the nucleus to the e- pair to be shared.


    • For A-level you are expected to be able to identify hybridization for small molecules which use up to about the 3p subshell, and also for all organic molecules in this syllabus. You will likely need to bring up hybridization when you are told to discuss molecular shapes and bond angles.

      As for promotion, that will be molecules with an empty p subshell (like carbon atoms do) or for period 3 elements like P and S
      e.g. H3PO4 or SF6) which can promote e- into the nearby empty 3d subshell. Also for transition elements which can promote into the nearby 4s and 4p subshells.

      Hybridization for transition metals is never asked for as far as I am aware, but shapes yes, octahedral, tetrahredral etc..


    • Molecular orbitals are simply combinations of atomic orbitals. They result when atoms combine together to form molecules…
      The molecular orbitals that form have different shapes, and v. importantly, different new energies!


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