<p>Do we need to memorize the bond angles for different molecular shapes? What other shapes do we need to know besides tetrahedral, trigonal pyramidal, bent, trigonal planar and linear?</p>
<p>honestly for the SAT subject test, that stuff barely comes up, just memorize the very basic sp bonding structures and you’ll be fine.</p>
<p>The chance that a question will specifically ask about the bond angles of a structure is pretty slim… But I would still know them, because really it’s not that hard, and it’s sometimes kind of useful. The angles are all exactly what you would expect them to be. (Linear is 180 degrees, trigonal planar is 360/3 = 120 degrees, and same logic for all the other structures, with electron pairs making the angles slightly less than the expected number)</p>
<p>^^^^^^^^^^^ tetrahedral- 109.5 degree for bond angle. how is the same logic used??</p>
<p>At the very most, you might see one question. Just remember that the only ones that don’t follow logical trends (besides the ones you definitely won’t be asked about, e.g. square pyramidal) are tetrahedral and trigonal-pyramidal, which are both ~109.5</p>
<p>If you see a shape-related question, it will most likely be asking what shape the molecule is. You can memorize it by hybridization, but I’m terrible at that, so I always just thought of it in terms of pairs of unshared electrons the central atom has.</p>
<p>Oh, it’s true that tetrahedral is somewhat different because it’s not planar… but like Somestudent2 said, if you just remember the few that aren’t really easy to see just by imagining the structure, you’ll be fine. Anyway, everything is basically either 180, 90, 120, or 109.5 degrees, so if you imagine the structure you could still probably guess the angle.</p>