For drawing questions, there are some things to be aware of to ensure that your answers are graded properly.
Always draw connections
The molecule drawing module grades connections, not the visual representation of the molecule. That means you can draw your molecules in any orientation, but you must indicate all connections; you can't simply draw two overlapping lines and expect the system to know you meant for there to be a carbon atom in the middle.
To help remind you how this works, "hidden" carbon atoms are indicated with light gray dots in graded molecules. If you don't see a gray dot, the system doesn't see a carbon atom.
Normally, hydrogen atoms attached to carbon atoms do not have to be shown. You may add them if you like (just be sure to add the correct number). The grading options within the drawing module will tell you if hydrogen atoms must be included on carbon atoms.
Hydrogen atoms must always be included on any non-carbon atom. A common source of mistakes is forgetting to add the hydrogen atom(s) (and/or charge) on atoms such as oxygen and nitrogen.
There are two ways to add hydrogen atoms to a non-carbon atom (X):
- Draw the X-H bond, as shown with the O-H group below, or
- Use the add hydrogen atoms button to change an X atom into an XHn group, as shown with the NH2 group below. (Note: the button may be disabled in some questions).
Lastly, remember that implicit hydrogen atoms attached to achiral carbons are optional, but if you include them you must do so correctly.