isotopesincluding

Isotopes are variants of a particular chemical element which differ in neutron number, and consequently in nucleon number. All isotopes of a given element have the same number of protons in each atom. Since the number of protons determines the chemical properties of an element, isotopes of an element are chemically nearly identical. They differ, however, in their mass and nuclear properties.

The number of protons in an atom is its atomic number, denoted by Z. This number uniquely identifies a chemical element. For example, all atoms with 6 protons are carbon atoms. The mass number of an atom, denoted by A, is the total number of protons and neutrons in its nucleus. The number of neutrons in an atom is given by N = A - Z.

Isotopes are often denoted by appending their mass number to the element's name or symbol. For instance, the most common isotope of carbon has a mass number of 12, so it is called carbon-12 or C-12. It has 6 protons and 6 neutrons. Another well-known isotope is carbon-14, with 6 protons and 8 neutrons.

Most elements found on Earth occur as a mixture of isotopes. The relative abundance of each isotope in this mixture is typically constant. For example, natural chlorine is a mixture of about 75% chlorine-35 (17 protons, 18 neutrons) and 25% chlorine-37 (17 protons, 20 neutrons).

Some isotopes are unstable and undergo radioactive decay, transforming into different isotopes or elements over time. These are called radioactive isotopes or radioisotopes. Unstable isotopes have a characteristic half-life, which is the time it takes for half of a sample of the isotope to decay. Stable isotopes do not decay. Understanding isotopes is crucial in fields like nuclear physics, chemistry, geology, and medicine.