The amphogens or chalcogens They are chemical elements that belong to the oxygen group or family of the periodic table. They are in group VIA o 16, located on the right side or block p.
The head of the group, as its name implies, is occupied by the element oxygen, which differs physically and chemically from its elements of the same group. The word 'chalcogen' derives from the Greek word chalcos, what does copper mean.
Many chemists have named these elements as formers of ash, chalks, bronzes, and chains. However, the most correct interpretation corresponds to that of 'mineral formers'.
Thus, chalcogens are characterized by being present in innumerable minerals; such as silicates, phosphates, oxides, sulfides, selenides, etc..
On the other hand, the word 'antigen' means capable of forming acidic or basic compounds. A simple example of this is in the fact that there are acidic and basic oxides.
Oxygen can not only be found in the air you breathe, but it is also part of 49% of the earth's crust. Therefore, it is not enough to look at the clouds to have it head on; and to contemplate the maximum physical manifestation of chalcogens, it is necessary to visit a mountain or an ore.
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What are the elements of group 16? The upper image shows the column or group with all its elements, headed by oxygen. Naming them in descending order we have: oxygen, sulfur, selenium, tellurium and polonium.
Although it is not shown, below the polonium is the synthetic, radioactive element, and the second heaviest after oganeson: livermorio (Lv).
Oxygen is found in nature primarily as two allotropes: Otwo, molecular or diatomic oxygen, and O3, ozone. It is gas under terrestrial conditions and is obtained from the liquefaction of air. In liquid state, it has pale bluish tones, and in the form of ozone it can form reddish-brown salts called ozonides..
It naturally presents twenty different allotropes, the most common of all being the S8 "The crown of sulfur." Sulfur is capable of forming with itself cyclic molecules or helical chains with covalent bond S-S-S…; this is known as catenation.
Under normal conditions it is a yellow solid, whose reddish and greenish colorations depend on the number of sulfur atoms that make up the molecule. In the gas phase, only, it is found as a diatomic molecule S = S, Stwo; similar to molecular oxygen.
Selenium forms shorter chains than sulfur; but with sufficient structural diversity to find allotropes of red, greyish crystalline, and amorphous black.
Some consider it a metalloid, and others a non-metallic element. Surprisingly, it is essential for living organisms, but at very low concentrations..
Tellurium, on the other hand, crystallizes as a grayish solid and possesses characteristics and properties of a metalloid. It is a very scarce element in the earth's crust, being found in extremely low concentrations in rare minerals.
Of all the chalcogens, it is the only metallic element; but like its 29 isotopes (and others) it is unstable, highly toxic, and radioactive. It is found as a trace element in some uranium minerals and in tobacco smoke.
All chalcogens have the same electronic configuration: nstwonp4. They therefore have six valence electrons. Being in block p, on the right side of the periodic table, they tend more to gain electrons than to lose them; therefore, they gain two electrons to complete their valence octet, and consequently acquire a valence of -2.
Likewise, they can lose all their six valence electrons, leaving them with a state of +6.
The possible valence states for chalcogens vary from -2 to +6, these two being the most common. As one moves down the group (from oxygen to polonium), the tendency of the elements to adopt positive valence states increases; which is equal to an increase in metallic character.
Oxygen, for example, acquires a valence state of -2 in almost all its compounds, except when it forms bonds with fluorine, forcing it to lose electrons due to its higher electronegativity, adopting a valence state of +2 (OFtwo). Peroxides are also an example of compounds where oxygen has a valence of -1 and not -2.
When you go down the group, the atomic radii increase, and with them the chemical properties of the elements are modified. For example, oxygen is a gas, and thermodynamically it is more stable as a diatomic molecule O = O, than as an "oxygen chain" O-O-O-O ...
It is the element with the highest non-metallic character of the group and, therefore, forms covalent compounds with all the elements of the p block and with some transition metals.
The non-metallic character decreases as the metallic character increases. This is reflected in the physical properties such as boiling and melting points, which increase from sulfur to polonium..
Another characteristic of the increase in metallic character is the increase in the crystalline configurations of the compounds formed by tellurium and polonium..
Some compounds formed by chalcogens are mentioned in a general way below..
-HtwoOR
-HtwoS
According to the IUPAC nomenclature, it is named as hydrogen sulfide, and not sulfur hydride; since H lacks a valence of -1.
-HtwoI know
Likewise, it is named as hydrogen selenide, like the rest of the hydrides.
-HtwoTea
-HtwoPo
Oxygen hydride is water. The others are smelly and poisonous, the H beingtwoS the best known of all, even in popular culture.
They all have the anion S in commontwo- (the simplest). Among them are:
-MgS
-FeS
-CuFeStwo
-NatwoS
-BaS
Similarly, there are selenides, Setwo-; telenuros, youtwo-, and polonuros, Potwo-.
Chalcogens can form compounds with halogens (F, Cl, Br, I). Some of them are:
-TeItwo
-StwoFtwo
-OFtwo
-SCltwo
-SF6
-SeBr4
Finally there are the oxides. In them, oxygen has a valence of -2, and they can be ionic or covalent (or have characteristics of both). You have, for example, the following oxides:
-SWtwo
-TeOtwo
-AgtwoOR
-FaithtwoOR3
-HtwoO (hydrogen oxide)
-SeO3
There are hundreds of thousands of other compounds, which involve interesting solid structures. In addition, they can present polyanions or polycations, especially in the cases of sulfur and selenium, whose chains can acquire positive or negative charges and interact with other chemical species..
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