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How do covalent bonds of the same molecule form?

  1. Jul 23, 2016 #1
    There is no difference in electronegativity, so how do bonds form?

    Take for example C-C, they both want 4 electrons for a full valence shell to become more stable - they meet each other, but how come they share 4 electrons? There is no difference in electronegativity for them to attract each other.

    Also - can atoms only bond to themselves when they have half a valence shell full of electrons? E.g. carbon can bond to itself because it has 4 valence electrons but also needs 4 so another carbon fills its valence shell perfectly.

    Apologies if any parts of my question confuse you, I just started chemistry so I don't have a solid grasp on these concepts.
  2. jcsd
  3. Jul 23, 2016 #2

    Simon Bridge

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    Covalent bonds form when atoms share electrons ... physically the configuration with the shared electrons has a higher binding energy than the configuration without, so atoms want to be in them. It's quantum. You typically don't get to know the process in detail until your third year.
  4. Jul 23, 2016 #3
    If you consider the noble elements, there is also the London forces (also called van der Waals' forces) to consider.
  5. Jul 24, 2016 #4
    The bonding results from electrons being attracted to both nuclei at the same time.
    Since each C atom has an incomplete shell the electrons of the other atom can approach its nucleus.
    Promotion of 2s -> 2p enhances the effect.
    For full shell atoms Pauli repulsion prevents this. In such a case there is only the much weaker Van der Waals interaction.
  6. Jul 25, 2016 #5

    That's what I like to hear. Thanks.
  7. Jul 25, 2016 #6

    Simon Bridge

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    No worries.
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