A Level Chemistry OCR Practice Exam

What does a skeletal formula illustrate in organic chemistry?

1. A detailed structural representation of all atoms in a molecule

2. A simplified structure showing only carbon skeletons and functional groups

3. A three-dimensional representation of molecular geometry

4. A formula that shows all hydrogen atoms explicitly

The correct answer is: A simplified structure showing only carbon skeletons and functional groups

A skeletal formula is specifically designed to provide a clear and simplified representation of organic molecules. It illustrates the carbon skeleton, which is the backbone of the molecule made up of carbon atoms connected by bonds. In this representation, the carbon atoms are often implied by the vertices of the lines (or ends of lines) rather than explicitly drawn. Functional groups, which are specific groups of atoms that impart characteristic properties to molecules, are typically shown explicitly in the skeletal formula. This approach allows chemists to easily visualize the essential structure and reactivity of the compound without the clutter of displaying every atom, particularly hydrogen, which is usually omitted unless it's critical to understanding the structure. This clarity and simplicity make skeletal formulas particularly useful for quickly conveying the overall structure of organic compounds in a concise manner. Other potential representations, such as detailed structural formulas or three-dimensional models, would either overwhelm with information or fail to highlight important aspects of the molecule’s function and connectivity as effectively as a skeletal formula does.