Isotopes can be thought of as the variants of a given chemical element that share the same atomic number, but have different mass numbers. The term ‘isotope’ is known to have Greek roots and can be roughly translated as “equal place”. The term ‘isotope’ was first used by the Scottish writer Margaret Georgina Todd in the year 1913. Some important concepts associated with isotopes and the different isotopes of the element hydrogen are discussed in this article.
Isotopes – An Introduction
All isotopes of an element will share the same nucleon number but will vary in neutron numbers. The nucleon number indicates the total number of protons in a chemical element’s nucleus and the total number of electrons that are dispersed around its nucleus. Thus, the isotopes of elements will feature different numbers of neutrons but the same number of protons and electrons. Furthermore, it can be noted that the multiple isotopes of a given element will all share the same atomic number but will vary in terms of mass number. The mass number of an atomic species is calculated by adding the total number of protons and the total number of neutrons that are held by the atomic nucleus of that chemical species. A common example of isotopes can be observed in the element carbon. The isotopes carbon-14, carbon-13, and carbon-12 all have the same atomic number, which is 6. All these isotopes contain a total of 6 protons in their atomic nuclei. However:
- The carbon-12 isotope is known to have a mass number of 12. This is accounted for by a total of 6 protons and 6 neutrons.
- The carbon-13 isotope is known to have a mass number of 12. This is accounted for by a total of 6 protons and 7 neutrons.
- The carbon-14 isotope is known to have a mass number of 12. This is accounted for by a total of 6 protons and 8 neutrons.
It can also be noted that the most abundant isotope of carbon on the planet Earth is the carbon-12 isotope.
Isotopes of Hydrogen
There are primarily 3 isotopes of hydrogen, namely protium, deuterium, and tritium. From the isotope definition, it can be understood that these three isotopes of hydrogen will vary in mass number despite sharing the same atomic number. Some key features of these three isotopes with regards to their nucleon numbers and neutron numbers are provided below.
- The hydrogen-1 isotope, also known as protium, is known to have a mass number of 1. This is accounted for by a total of 1 proton and 0 neutrons.
- The hydrogen-2 isotope, also known as deuterium, is known to have a mass number of 2. This is accounted for by a total of 1 proton and 1 neutron.
- The hydrogen-3 isotope, also known as tritium, is known to have a mass number of 3. This is accounted for by a total of 1 proton and 2 neutrons.
Thus, the three key isotopes of hydrogen – protium, deuterium, and tritium – feature a total of 0, 1, and 2 neutrons respectively.