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I am trying to teach myself about Electron Ionization, and am very confused about the formation of the CH4+ Ion.

enter image description here

Do the dotted lines between the C and the H, and between the two Hydrogens indicate a resonance structure of sort? I have taken organic chemistry, but cannot wrap my head around this.

Archer
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HSB
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  • https://chemistry.stackexchange.com/questions/68849/how-does-a-5th-hydrogen-bind-to-carbon-atom-in-ch5 https://chemistry.stackexchange.com/a/32326/9961 – Mithoron Sep 03 '18 at 21:16
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    Dotted lines indicate three center bonds, which can be viewed as a sort of resonance. – Mithoron Sep 03 '18 at 21:19

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The dotted lines in this structure could be thought of as partial bonds. In other words, none of those three bonds has a bond order of 1 with two electrons attributable to that bond.

Another way to look at this structure is that the dashed lines represent multicenter bonding. A common example of multicenter bonding is diborane $\ce{B2H6}$. The structure of diborane features 3-center-2-electron bonds (often abbreviated 3c2e bonds - in this notation, a typical single sigma bond is a 2c2e bond) with two hydrogen atoms shared by both boron atoms: enter image description here

These bonds in $\ce{CH4+}$ could be considered a 3-centered-3-electron bond as originally each C-H bond would have had two electrons. The radical cation is one electron short, so there are only three electrons shared between those three atoms.

Ben Norris
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    Afaik there's no 3c3e - there's normal 3c2e in CH4 cation and unpaired electron. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC23401/ – Mithoron Sep 04 '18 at 17:03