Molecular Formulas & Bond-Line Structures

Guidance on how to use this assignment:

• In this assignment students will learn how to determine molecular formulas from bond-line structures.
• This assignment gives students the opportunity to practice this technique, which they will use for the rest of their time in the course, and potentially longer, since the vast majority of chemical structures are communicated via their bond-line structure.
• Students can spend 10-20 minutes in class on this exercise, and then finish any remaining work at home.

Learning Objective(s)

After completing this assignment, students will be able to:

• Determine the molecular formula for complex organic molecules without counting out every (hydrogen) atom in the structure.  
• This shortcut is useful when determining whether or not compounds are structural isomers, and when analyzing mass spectra (where the structures, formulas, and masses of many different fragments need to be determined).

Assignment completion instructions

Planning

• What will the instructor need before the activity?
• Printed copies of this worksheet, unless students all have devices that will allow them to mark up the PDF copy in class.
• What will the student need before the activity?
• Tools: a writing implement or a device that will allow them to mark up a PDF copy of the assignment.
• Training: The student should understand how to draw and interpret bond-line structures for compounds with or without formal charges.  
• Time: the assignment should take 10-20 minutes
•  Source Material(s) for the activity (created by or provided by the instructor)

Answer Keys (answers are shown in red)