Many of my students get chlorine $\ce{Cl}$, confused with carbon monoiodide $\ce{CI}$, despite my promises to use serif fonts whenever possible and to never give them carbon monoiodide in a question.

Everything I know about chemical bonding tells me carbon monoiodide should not exist ($\ce{CI4}$, sure), but weird things happen sometimes. My only results from internet searches for carbon monoiodide bring up a set of Quizlet flash cards.

Will my students prove me wrong if I tell them that carbon monoiodide does not exist (except possibly in extreme laboratory conditions).

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    $\begingroup$ Impossible to prove a negative so for the moment a comment rather than a answer as I can't provide a reference. No, a simple diatomic CI molecule does not exist as something you can put in a bottle and use later. Compounds with the stoichiometry CI do exist, such as C2I2 (sciencemadness.org/member_publications/diiodoacetylene.pdf) but that's as close as you can get. But personally I think the kids are taking the proverbial. $\endgroup$
    – Ian Bush
    Nov 25 '18 at 11:04
  • $\begingroup$ Define "exist." $\endgroup$
    – Zhe
    Nov 26 '18 at 18:40
  • $\begingroup$ If carbon monofluoride it seems likely that carbon can bond singly with any of the halogens, even if the molecule is highly reactive or unstable. $\endgroup$
    – Sean Lake
    Sep 5 '19 at 7:19

Provided that mellitic anhydride ($\ce{C12O9}$, empirical formula $\ce{C4O3}$) is considered one of carbon oxides, then e.g. hexaiodobenzene ($\ce{C6I6}$, empirical formula $\ce{CI}$) could be considered a form of carbon(I) iodide, formally. But please rather don't teach that in regular lectures.



Formula:    CI
Element System: C-I
Element Names:  Carbon, Iodine
Molecular Weight:   138.915 g/mol
Name(s):    CI <g>
Carbon Monoiodide gas

See: http://lb.chemie.uni-hamburg.de/static/ES/2_C_C-I.php?content=527/pz0cDmNo

  • 1
    $\begingroup$ Then there are carbon monoxide and cobalt to confuse them. There are some fonts, though, such as those designed for computer source, that do a better job of distinguishing 1 and l, O, o and 0. $\endgroup$ Nov 25 '18 at 5:59

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