Radiation Safety Practice Exam

The smallest unit of a compound that still retains the unique physical and chemical characteristics of the compound is a?

1. Atom

2. Molecule

3. Element

4. Ion

The correct answer is: Molecule

A molecule is the smallest unit of a compound that retains the unique physical and chemical properties of that compound. This means that when the bond between atoms within a molecule is broken, the distinct characteristics that define the compound are lost, as it can no longer function as a cohesive entity. Molecules are formed when two or more atoms are chemically bonded together, and it is this arrangement of atoms that gives rise to the properties of the compound. For example, a water molecule (H2O), consisting of two hydrogen atoms and one oxygen atom, exhibits properties such as being a liquid at room temperature and having a high specific heat capacity – characteristics that are unique to water. In contrast, while an atom is a basic unit of matter, it does not represent a compound, as it can exist independently and does not exhibit the characteristics of the compounds formed when atoms bond together. Elements are pure substances consisting of only one type of atom and cannot form compounds on their own. An ion is an atom or molecule that has gained or lost one or more electrons, resulting in a positive or negative charge, but it does not represent a whole compound. Therefore, the correct identification of a molecule as the fundamental unit of a compound highlights its role in maintaining the specific