Final answer:
Calcium and phosphorus are the elements that are components of bone and required for metabolic reactions. They contribute to bone hardening and the synthesis of mineral crystals within bone, and are also needed for building bones and teeth.
Step-by-step explanation:
The elements that are components of bone and are required for metabolic reactions are calcium and phosphorus. These elements are present in the skeleton and necessary for the hardening of bones. The bonding of calcium, phosphorus, and other elements produces mineral crystals that are found in bone, which is an example of a synthesis reaction. Calcium and phosphorus are also needed to build bones and teeth, and they serve as a mineral reserve for the body. Inadequate calcium can contribute to osteoporosis, a condition in which bones become porous and brittle.