Calcium is an example of -a heterogeneous mixture. both an element and pure substance. -a homogeneous mixture. both a compound and pure substance.

To determine the correct classification of calcium, let's analyze the options provided: 1. **Heterogeneous mixture**: A heterogeneous mixture consists of different components that can be physically separated. Calcium is not a mixture; it is a pure substance. 2. **Both an element and pure substance**: Calcium is indeed an element, as it is found on the periodic table with the symbol "Ca." It is also a pure substance because it consists of only one type of atom. 3. **Homogeneous mixture**: A homogeneous mixture has a uniform composition throughout. Calcium is not a mixture; it is a pure element. 4. **Both a compound and pure substance**: A compound consists of two or more different elements chemically combined. Calcium is not a compound; it is a single element. Based on this analysis, the correct answer is: **Both an element and pure substance.**