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My 7 year old nephew found a chemistry text book and started copying some pictures and diagrams. He drew this and asked me what do the asterisks mean ? He said he normally sees letters which means atoms. But he can't found an atom that called "asterisks" from the periodic table.

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learningtech
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    Asterisk some times indicates an excited molecule in spectroscopy. It is not an element. In this particular case, this asterisk appears to have a decorative purpose only. – AChem Nov 27 '21 at 17:47
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    Your nephew is apparently showing a polymer, with -CH2-CH2- repeating units. – AChem Nov 27 '21 at 17:48
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    We shall commit to enroll him in a couple of years – Alchimista Nov 27 '21 at 19:37
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    It is not an asterisk. It means "repeating the central unit -CH2-CH2- a lot of times, without any changes". – Maurice Nov 27 '21 at 20:53
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    @Alchimista, he seems more prepared now that many other questioners. "Give me the child and I'll give you the chemist," as Aristotle stated (or was it Democritus? Dalton??). – DrMoishe Pippik Nov 28 '21 at 00:45
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    M. Farooq gave answer in his comment above as: ``` Your nephew is apparently showing a polymer, with -CH2-CH2- repeating units.
    – learningtech Nov 28 '21 at 01:04
  • Not sure you shall tell him, perhaps just a note for you. The way it is represented is somewhat technological, as it stress that the original monomer had 2 C. Once formed, the polymer can be represented as - (CH2) -. The same happens with names, most accepted names refer to the starting material rather than the formal repeating unit. Another note, the terminals would be some other groups. – Alchimista Nov 28 '21 at 07:35
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    FWIW, the red dots are meant to represent the valence electrons. In this structure, all the valence electrons are bonding electrons (involved in bonds). One pair of bonding electrons shared between two atoms gives a single covalent bond. Two pairs of shared electrons gives a double bond, etc.. All the bonds in this molecule are single bonds. You should ask him to double-check the picture in his book. I believe he has an extra pair of bonding electrons between the two carbons. This causes each carbon to be surrounded by 10 valence electrons, when it should be eight. – theorist Nov 28 '21 at 09:38
  • "I told my nephew, and then my nephew replied, "oooh!!! It's because you can't put infinite number of polyethene in this book! It will be TOO BIG! Bigger than the universe!" I think your nephew misunderstood "repeating". It sounds like he took it to mean infinitely repeating. That's obviously not the case with a real molecule. Thus the reason the entire polymer structure can't fit onto the page is because it is big, not because it is infinite. Plus, conceptually, once you've show that it's repeating, there's no reason to show more units, because they're just more of the same. – theorist Nov 28 '21 at 09:47
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    @theorist though theorists model conjugated polymers as infinite chains, it please them and makes everything more fancy. :) – Alchimista Nov 28 '21 at 10:40
  • @Alchimista I work with biopolymers rather than conjugated synthetics, but I actually model mine as finite chains. So maybe that means I'm at least partially grounded in the real world :). – theorist Nov 28 '21 at 22:27

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