Question: how many valence electrons are present in an ethyne molecule?
Answer: Drawing the Lewis Structure for C2H2 (Ethyne or Acetylene) For C2H2 you have a total of 10 valence electrons to work with. In drawing the Lewis structure for C2H2 (also called ethyne) you'll find that you don't have enough valence electrons available to satisfy the octet for each element (if you use only single bonds).