Isotopes are variants of a particular chemical element which differ in neutron number, although all isotopes of a given element have the same number of protons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος"place"), meaning "the same place". The number of protons within the atom’s nucleus is called the atomic number. Each atomic number identifies a specific element, but not the isotope; an atom of a given element may have a wide range in its number of neutrons. The number of both protons and neutrons in the nucleus is the atom's mass number, and each isotope of a given element has a different mass number.
Stable isotopes are generally defined as non-radioactive isotopic elements that do not decay over time. Radioactive isotopes may also be classified as stable isotopes when their half-lives are too long to be measured. These elements can often be found to occur in nature and include isotopes of carbon, nitrogen, hydrogen, oxygen, noble gases and metals.
For example, there are a lot of carbon atoms in the universe. The normal ones are carbon-12. Those atoms have 6 neutrons. There are a few straggler atoms that don't have 6. Those odd ones may have 7 or even 8 neutrons. Carbon-14 actually has 8 neutrons. C-14 is considered an isotope of the element carbon.
A naturally occurring radioactive isotope of carbon having six protons and eight neutrons in the nucleus. The isotope Carbon-14 is essential in the research of archaeological and biological remains by radiocarbon dating. C-14 does not last forever. There is a time when it loses its extra neutrons and becomes C-12. The loss of those neutrons is called radioactive decay. That decay happens regularly like a clock. For carbon, the decay happens in a few thousand years. Some elements take longer, and others have a decay that happens over a period of minutes. Archeologists are able to use their knowledge of radioactive decay when they need to know the date of an object they dug up in a process called carbon dating.
It is an isotope because it contains a different number of neutrons from the element iodine. Normal iodine has a mass number of 127, so iodine-131 has 4 more neutrons. It has been found useful in radiation treatments for thyroid cancer treatment. Your thyroid gland absorbs nearly all of the iodine in your body. When radioactive iodine is taken into the body in liquid or capsule form, it concentrates in thyroid cells. The radiation can destroy the thyroid gland and any other thyroid cells, including cancer cells that take up iodine, with little effect on the rest of your body. Radioactive iodine therapy improves the survival rate of patients with thyroid cancer.
An isotope of hydrogen and is used to make things such as clock faces and wristwatches glow in the dark. Tritium provides an extremely bright self-activated, self-sustaining light source that will stay bright throughout the night and has a life span of twenty years.
Atomic Mass Formula
Radioactive Half-Life Formula
Experimental Data and Atomic Structure