The Greek word isobarḗs, which refers to that “Of equal weight”, it came to French as isobare. He arrived in our language as isobaro or isobarus, as accepted by the Royal Spanish Academy (RAE).
The concept is used in the field of meteorology to name two or more sites with the same mean atmospheric pressure. Isobar is also called line that, in a meteorological map, allows to unite those places that have identical atmospheric pressure at a specific moment.
To understand what isobars are, in this way, one must first focus on the notion of atmospheric pressure. This is the name given to the pressure exerted by the atmosphere on all the bodies that are in it. The atmospheric pressure considered normal is 1013 mbar or 760 mm Hg at the sea level.
In the field of chemistry, on the other hand, isobars are those atoms that have the same mass number, although different atomic number. This means that they are atoms of various chemical elements, with different chemical properties. In addition, they come from different chemical elements.
The mass number or mass number it reflects the sum of the number of protons and neutrons in the nucleus of the atom. The atomic number, meanwhile, refers specifically to the number of protons.
It should be noted that the net number of protons and neutrons found in each nucleus does not vary. In other words, the origin of a species Isobar occurs when two atomic nuclei exhibit the same net number of protons and neutrons for their respective species.
Despite this, the number of protons and neutrons that make up this total is different. To be able to visualize this graphically, it is possible to take a look at the mass number, which in the periodic table is found in the upper left corner of the symbols of chemical elements: in two isobars, this value is identical.
It is important not to confuse isobars with isotopes. Isotopes are atoms with the same atomic number and different mass numbers (unlike isobars): that is why they have the same chemical properties and belong to the same chemical element. The isotonesThey also have different atomic numbers and different mass numbers.
Regarding the etymology of the word isobarus, its origin dates back to the Greek language, where we find the components isos and baros, which mean “equal” and “pesos«, Respectively. This refers us once again to the equality of weights that exists between the pairs of nuclear species that can be classified in this way. We can observe the first of these components in the other related terms.
Another of the species with which the Isobars have some similarities with respect to their cores is that of the isotones, which are briefly mentioned in a previous paragraph. Among the coincidences they have is the number of neutrons, which is the same; However, the atomic number and the mass number are different, something that can be seen in several pairs of elements.
We must also take into account the word nuclide, which is used to name the different possible groups of nucleons, the structures which are made up of protons and neutrons. The nuclides, therefore, can be differentiated by the number of protons or neutrons, or also by the amount of energy that is appreciated in the structure of their conglomeration.
The use of the term isobars to denote species considered nuclides with the same number of nucleons (that is, having the same number of mass) was proposed by a chemist from Great Britain named Alfred Walter Stewart in the 1910s.