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So far I have been taught that everything wants to achieve noble gas configuration - 8 electrons in the outer shell.

I came across a methyl cation. Which contains a positive carbon, no lone pairs and 3 bonding pairs of electrons so 6 electrons in total. 6 electrons are obviously less than 8 electrons so how can it exist as it defies apparently the rules I have been taught.

Thanks,

Daniel

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    $\begingroup$ Some say humans can't fly. In fact they can, but not for long. Same thing here. $\endgroup$
    – Ivan Neretin
    Oct 8, 2019 at 14:03

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The way you put it that everything wants to achieve noble gas configuration is a good rule of thumb for predicting molecules that are stable and long-lived. However, not everything is in equilibrium. A methyl cation certainly exists, and it certainly wants to achieve the noble gas configuration, but it still takes time to do so. So we can conclude that the methyl cation is an unstable, short-lived, highly reactive molecule, which is true. And you are totally right to explain this with the tendency of having a closed electronic shell.

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  • $\begingroup$ Requiring every atom to simultaneously have a noble gas configuration does not always work. Cyclopropenyl cation doesn't have that when you draw the Lewis structure(s), the anion does; yet it is the cation which (at least if chilled slightly) is indefinitely stable. $\endgroup$
    – Oscar Lanzi
    Oct 8, 2019 at 14:49

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