Isotopes are nothing but varied versions of the same atom. In other words, the number of protons in isotopes is the same, but the neutron count may differ across variants. This means the different isotopes of an atom have the same atomic number but different mass numbers and masses, since an atom’s mass number is ascertained by its neutron population. Proton strength is the same as it’s the number defining the atom or compound. Not all elements have isotopes, but most do. Sodium, beryllium, phosphorus, aluminium, manganese, iodine, gold, arsenic, niobium, and yttrium have only one stable isotope.

Generally, a single element’s isotopes have almost identical chemical properties. Hydrogen is the only element with different names for its isotopes, since the isotopes are quite distinct from each other. Protium, deuterium, and tritium are three naturally occurring isotopes of hydrogen. The number of protons across the three isotopes is the same, which is 1. However, the neutron number differs, which is protium (0 neutron), deuterium (1 neutron), and tritium (2 neutrons). If the proton numbers were different, the hydrogen atom will no longer be a hydrogen atom.

Types of Isotopes

An isotope can be radioactive or stable. An unstable isotope, a radioactive isotope can transform into a stable isotope of another element. In other words, the isotope’s nucleus is not stable and emits excess energy as alpha, gamma and beta rays. For instance, the isotope uranium-238 gives out alpha particles, and turns into the isotope lead-206. A stable isotope, as the name suggests, is steady and would remain the same in the future.

An element can have both stable and radioactive isotopes. All chemical elements have one or more radioactive isotopes. However, some elements such as technetium do not have a stable isotope.

Nucleon Number

Nucleon number – the sum of the neutrons and protons in the nucleus of an atom – defines an element’s isotope. An element’s isotope can be denoted either by a preceding superscript or a superscript written after the element symbol on the periodic table. For example, the nucleon number of carbon can either be written as 14 C, carbon-14 or C-14. C-12 is another carbon isotope. Both carbon 14 and carbon 12 have six protons, but eight and six neutrons, respectively.