The reason why the balancing ions are often left off, I think, is not due to simple laziness but also for a desire to avoid confusion by focusing on specifics. Charge is always conserved, and balanced: the presence of a charge implies the existence of an equal and opposite charge somewhere else. ![]() The charge IS there, it just hasn’t been drawn in. It’s a signal that “suddenly the charges aren’t that important”, or even worse, they aren’t there. Students coming out of gen chem where they have had to balance these massive redox equations often get confused when they notice their instructor (or the textbook) not balancing charges anymore. The subject of counterions also causes a lot of confusion. You’re just supposed to know that the negative charge represents a pair of electrons on the atom.įinally, if you see a positive charge on carbon, you’re supposed to know that not only are there zero lone pairs on the carbon, there are only 3 bonds. Using the curved arrow notation, you’ll often see the tail of an arrow coming from a negative charge on a given atom. The atom that causes the most confusion on this point is probably carbon when it is drawn with a negative charge: the negative charge implies the existence of a lone pair. (If you don’t understand formal charge by this point, tsk tsk : this is a core skill). How do you know how many to draw? If you understand formal charge, this should be a snap. Like hydrogens, you’re “just supposed to know that they’re there”. Again, this is a time-saving measure, but also they tend to get in the way and clutter up the structure. Lone pairs are often not drawn on structures either. Why? Because we omit drawing in all the pesky little hydrogens. The key thing in recognizing hidden hydrogens is that wherever you see less than 4 bonds to carbon, that carbon is going to have hydrogens attached such that there’s a full octet. And it’s not hard to see why: they’re a snap to draw. Line drawings are the chemists’ method of choice for depicting structures. The key is learning to recognize the things that “you’re just supposed to know are there”. ![]() There are 3 common types of shortcuts that organic chemists make when drawing structures. This post is about the shortcuts you have to know about when looking at chemical structures. ![]() From a distance, maybe an extra 10-20 seconds here or there might not sound like a lot to you, but you might be surprised by what people will do to shave 5 seconds of boredom off their journey. Drawing the full structures of chemical formulae out is a gigantic pain.
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