An element is uniquely determined by the number of proton s in the nuclei of its atom s. The number of protons in the nucleus of the atom of an element is known as the atomic number of that element. The number of electron s in the atom of a specific element can vary. If the number of electrons is the same as the number of protons, then the atom has no electric charge. However, if the number of electrons is different from the number of protons, the atom is called an ion. If there are more electrons than protons, it is a negative ion; if there are fewer electrons than protons, it is a positive ion. The number of neutron s in the atom of a specific element can also vary. The number of neutrons in the nucleus of an element determines the isotope of the element.
Building a higher peak bone mass early in life helps prevent osteoporosis later in life. It is essential to eat enough calcium-rich foods and do regular physical activity (high impact or weight bearing) during the first twenty years of life to help achieve a healthy maximum bone density.
Adequate intakes of calcium (500 mg per day or more) and of vitamin D in populations with high osteoporosis rates helps to reduce fracture risk, so does sun exposure and physical activity to strengthen bones and muscles.