Chemical Bonding

by Adam Le Gresley, PhD

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    In the previous lecture, we talked about electrons and orbitals—specifically, atomic orbitals—so, where electrons reside in their elemental form. And we touched briefly upon what happens in covalent bond formation—that is to say, electrons which want to achieve a low-energy state by forming a complete outer shell can share electrons. Well, what actually happens in that process? It isn't just a simple dot-and-cross diagram that perhaps you were familiar with when you were doing very early qualifications. There's actually more to it than that, and that is molecular bond formation. So let us take the simplest example: the molecule hydrogen. As I said to you before, many atoms don't exist in atomic form in nature; they exist in molecular or ionic form. And here we have the gas H2, or hydrogen. You'll be familiar with H2 potentially, but you won't be aware, necessarily, that what's happening in this scenario is that the electrons which are being shared are being shared as part of a molecular orbital. And that molecular orbital is represented here, in the center of the board, where you can see one hydrogen atom with an electron configuration of 1s1 sharing its electrons with another hydrogen atom, which also has an atom configuration of 1s1. By sharing electrons, the hydrogen now has, in both cases, a full outer shell—specifically, now 1s2. So, like helium, it has now become more stable. To make this happen, the sigma orbitals of… sorry, the s orbitals of the hydrogen overlap to form a sigma bond. And this changes the shape of our atomic sigma orbital... atomic s orbitals into our covalent sigma orbitals. The sigma orbital, as you can see here, is shown when one s orbital from a hydrogen overlaps with another s orbital from the hydrogen, and this forms, as...

    About the Lecture

    The lecture Chemical Bonding by Adam Le Gresley, PhD is from the course Chemistry: Introduction. It contains the following chapters:

    • Chemical bonding
    • Other Sigma bonds
    • Electronegativity
    • Hybridisation
    • pi Bonds
    • The double and triple bond

    Included Quiz Questions

    1. HF
    2. PH3
    3. NH3
    4. H2S
    5. HI
    1. two sp orbitals overlapping, two 2py overlapping and two 2pz overlapping
    2. an sp and sp2 overlapping and 2p orbitals overlapping
    3. an sp2 and sp2 overlapping and 2p orbitals overlapping
    4. two 2s orbitals overlapping
    5. one 2s and one sp2 orbital overlapping

    Author of lecture Chemical Bonding

     Adam Le Gresley, PhD

    Adam Le Gresley, PhD

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