The periodic table is one of the greatest creations of modern chemistry. Its objective is to bring order and give meaning to all the elements that we find in the universe.
A common question when we talk about the periodic table is usually: “How were the elements classified before the periodic table was developed?” The point is that the chemical elements have interested scientists for many centuries, but it was not until early 19th century so that the study of the elements and their classification would have great advances.
periodic table background
The first chemist to come to the conclusion that it was necessary to group and classify the different elements was the German Johann Wolfgang Dobereiner (1780-1849): conceived the idea of ordering them by triads, groups of three elements with similar and comparable properties. Later, in the mid-nineteenth century, the French geologist and mineralogist Alexandre-Émile Béguyer de Chancourtois He first classified the elements according to their atomic mass. For this he used some very complicated terms, which made his idea not very successful. Furthermore, we cannot forget that John Alexander Queen Newlands, English analytical chemist, was the first to publish a periodic table of the elements. He used to support his hypothesis the law of octaves; a chemical law that states the following: the chemical properties of the elements are repeated every 8 times. However, it was neither a German, nor a Frenchman, nor an Englishman, who conceived the contemporary periodic table. Had to wait for the arrival of the theories of a Russian chemist.
Dmitri Ivanovich Mendeleyev: father of the periodic table
Considered the father of the periodic table, Mendeleev He presented his idea of classifying elements in 1869; something inspired by the background that already existed and that I mentioned above. Mendeleev’s theory determined the following points:
- The properties of the elements are periodic if they are arranged according to their atomic mass.
- Elements that have properties Similar, they also have similar atomic masses.
- The arrangement of the elements is linked to their valences (number of electrons missing for an element to reach its maximum energy level).
- Common elements have, as a rule, a small atomic mass.
- The atomic mass is very important, since the character of the element depends on it.
- more elements they will be added to the table over time.
- It could happen that the atomic mass of an element varies.
- The properties of an element are derived from their atomic mass.
Mendeleev’s periodic table had 63 elements, and elements were added until the current number of 118 was reached.
Variation of the current periodic table
The current periodic table has been remodeled and is based on criteria somewhat different from those of Mendeleev’s table. For example:
- The elements of the current periodic table They are no longer classified according to their atomic mass, but are now classified by increasing atomic number.
- In the same column we place the elements that They have the same number of electrons in their outer shell. A criterion that does not stray entirely from Mendeleev’s classification.
- The current periodic table has 7 rows called periods and 18 columns that we call families.
Presentation of the current periodic table
The latest updates that have been carried out in the current periodic table date from the year 2016, when the International Union of Pure and Applied Chemistry (IUPAC), which represents the recognized authority for determining the rules and nomenclatures of the elements set some new features of the periodic table.
From the 2016 revision, the periodic table has 118 items, of which 83 are what we call “primordial” Also, the last 24 elements of the table are elements named “synthetics”, since they do not exist on our planet and have been created by man. Some elements that could be found in supernova explosions.
Element families of the periodic table
In the current classification of the periodic table, all elements in the same family have the same number of electrons in its outer shell, what makes them chemical elements with similar characteristics. That is to say, react with the same type of compound and, moreover, they form comparable molecules and ions. There are several families, let’s see some of the most important.
Alkali metal family
Lithium, sodium, potassium, rubidium, cesium and francium are included in this family. All these elements have an outer shell with one electron, and they all form cations by losing an electron. These are shiny, soft and highly reactive metals. It is precisely because of his high reactivity, that these metals must be preserved in mineral oil, so they are not found as is in nature. Of all, sodium is the most common alkali metal in nature.
family of alkaline earth metals
This family includes metals such as beryllium, magnesium, calcium, strontium, barium, and radium. All these elements have 2 electrons in its outer shell and, in addition, all of them form cations by losing two electrons Alkaline earth metals have a silver glitter characteristic, and its name comes from the word earth, in reference to the particular characteristic that these metals They can resist fire.
Lanthanide family
Formed by 15 elements, its name “lanthanide” It comes from the first of all the elements that make up this family: lanthanide. Is about shiny metals, capable of rapidly fogging in the open air and reacts rapidly in contact with water. A family of elements that includes some of the most relevant, such as lanthanum, cerium, gadolinium or the terbium.
actinide family
A family of elements that counts 15 elements, heavy metals that take their name from the parent material of the family: the actinium. The actinides are all very radioactive, in addition to being soft and with silver reflections. In this sense, we can cite uranium, plutonium or thorium.
family of transition metals
The family of transition metals is a family that includes many elements of particular electronic configuration. This is so because they are elements that have a great variety of colors and, in addition, great electrical conductors. This family includes metals such as rhodium, palladium, copper, platinum and titanium.
poor metal family
The family of poor metals has soft or brittle metals that tend to form covalent bonds. Some examples that we find in this family are aluminum, zinc, tin, mercury or lead.
metalloid family
The family of metalloids is a family of elements that have characteristics very particular. They look like metal, but they are actually brittle and are not capable of conducting electricity. Among these metalloids we find boron, silicon, arsenic or antimony.
family of nonmetals
The family of nonmetals is a family of elements that happen to be Excellent insulators, both thermal and electrical. Non-metals represent very necessary elements for planets where there can be life such as the Earth. Among them we find carbon, nitrogen, oxygen, sulfur, or chlorine.
Halogen family
The penultimate family of elements is that of the halogens, which includes elements such as fluorine, chlorine, bromine, iodine and astatine. to all these elements they lack one electron to complete their last shell.
family of noble gases
The last family corresponds to that of the noble gases. These gases also They are known as monatomic inert gases. and includes some of the most important gases in the universe: helium, neon, argon, krypton, xenon and radon. They all have a full outer shell that makes them little reactive, since they are not capable of forming ions, nor of participating in any molecule.
Who is the creator of the periodic table?
The contemporary periodic table was devised and structured by the Russian chemist Dmitri Ivanovich Mendeleev.