The subgroup of chalcogenes includes sulfur - this is the second of the elements that can form a large number of ore deposits. Sulfates, sulfides, oxides, other sulfur compounds are very widespread, important in industry and nature. Therefore, in this article we will consider what they are, what constitutes sulfur itself, its simple substance.
Sulfur and its characteristics
This element has the following position in the periodic system.
- Sixth group, the main subgroup.
- The third minor period.
- The atomic mass is 32.064.
- The serial number is 16, there are as many protons and electrons, there are 16 neutrons as well.
- Refers to non-metal elements.
- The formulas read as "es", the name of the element is sulfur, Latin sulfur.
In nature, there are four stable isotopes with mass numbers of 32.33.34 and 36. This element is the sixth most abundant in nature. Refers to biogenic elements, as it is part of important organic molecules.
The electronic structure of the atom
Sulfur compounds owe their diversity to the features of the electronic structure of the atom. It is expressed by the following configuration formula: 1s 2 2s 2 2p 6 3s 2 3p 4 .
The above order reflects only the stationary state of the element. However, it is known that if additional energy is given to the atom, then pairing of electrons at the 3p and 3s sublevels is possible, followed by the next transition to 3d, which remains free. As a result, not only the valency of the atom changes, but also all possible degrees of oxidation. Their number increases significantly, as does the number of various substances involving sulfur.
The degree of oxidation of sulfur in the compounds
There are several main options for this indicator. For sulfur, these are:
Of these, S +2 is most rarely found, the rest are dispersed everywhere. The chemical activity and oxidizing ability of the whole substance depend on the degree of oxidation of sulfur in the compounds. So, for example, compounds with -2 are sulfides. In them, the element we are considering is a typical oxidizing agent.
The higher the oxidation state in the compound, the more pronounced oxidizing abilities the substance will possess. This can be easily verified if we recall the two main acids that sulfur forms:
- H 2 SO 3 - sulphurous;
- H 2 SO 4 - sulfuric.
It is known that the latter is a much more stable, strong compound, which, in high concentration, has a very serious oxidation ability.
Simple substance
As a simple substance, sulfur is a beautiful yellow crystals of even regular regular shape. Although this is only one of its forms, because there are two main allotropic modifications of this substance. The first, monoclinic or rhombic - this is the yellow crystalline body, not able to dissolve in water, but only in organic solvents. It is distinguished by fragility and a beautiful shape of the structure, presented in the form of a crown. Melting point - about 110 0 .
If you do not miss the intermediate moment when heating such a modification, then you can timely detect another condition - plastic sulfur. It is a brown rubbery, viscous solution, which, upon further heating or rapid cooling, again turns into a rhombic shape.
If we talk about chemically pure sulfur obtained by repeated filtration, then it is a bright yellow small crystals, brittle and completely insoluble in water. Able to ignite in contact with moisture and oxygen. They are distinguished by a sufficiently high chemical activity.
Being in nature
In nature, there are natural deposits from which sulfur compounds are extracted and it itself as a simple substance. In addition, it contains:
- in minerals, ores and rocks;
- in the body of animals, plants and humans, as it is part of many organic molecules;
- in natural gases, oil and coal;
- in oil shale and natural waters.
You can name some of the richest sulfur minerals:
- cinnabar;
- pyrites;
- sphalerite;
- antimonite;
- galena and others.
Most of the sulfur produced today is spent on sulphate production. Another part is used for medical purposes, agriculture, industrial processes for the production of substances.
Physical properties
They can be described in a few points.
- It is insoluble in water, in carbon disulfide or turpentine - it is well soluble.
- With prolonged friction, it accumulates a negative charge.
- The melting point is 110 0 C.
- Boiling point 190 0 .
- Upon reaching 300 0 it passes into a fluid, easily mobile.
- Pure substance is capable of spontaneous combustion. Combustible properties are very good.
- The smell itself has practically no smell, but the hydrogen compounds of sulfur emit a pungent smell of rotten eggs. Just like some gaseous binary representatives.
The physical properties of the substance in question were known to people from antiquity. It is because of its combustibility that sulfur got its name. In wars they used asphyxiating and poisonous fumes, which are formed during the combustion of this compound, as a weapon against enemies. In addition, sulfur-containing acids have also always been of great industrial importance.
Chemical properties
Topic: "Sulfur and its compounds" in a school chemistry course takes not one lesson, but several. There are a lot of them. This is due to the chemical activity of this substance. It can exhibit both oxidizing properties with stronger reducing agents (metals, boron and others), and reducing with most non-metals.
However, despite this activity, only with fluorine the interaction occurs under ordinary conditions. For everyone else, heating is required. Several categories of substances with which sulfur can interact can be identified:
- metals;
- non-metals;
- alkalis;
- strong oxidizing acids - sulfuric and nitric.
Sulfur compounds: varieties
Their diversity will be explained by the unequal value of the oxidation state of the main element - sulfur. So, we can distinguish several main types of substances on this basis:
- compounds with an oxidation state of -2;
- +4;
- +6.
If we consider classes, and not an indicator of valency, then this element forms such molecules as:
- acids;
- oxides;
- hydrogen sulfur compounds;
- salts;
- binary compounds with non-metals (carbon disulfide, chlorides);
- organic matter.
Now consider the main ones and give examples.
Substances with oxidation state -2
Compounds of sulfur 2 are its conformations with metals, as well as with:
- carbon;
- hydrogen;
- phosphorus;
- silicon;
- arsenic;
- boron.
In these cases, it acts as an oxidizing agent, since all of the listed elements are more electropositive. Consider the most important of them.
- Carbon disulphide - CS 2 . Transparent liquid with a characteristic pleasant aroma of ether. It is toxic, flammable and explosive. It is used as a solvent, and for most types of oils, fats, non-metals, silver nitrate, resins and rubbers. It is also an important part in the production of rayon - viscose. It is synthesized in large quantities in industry.
- Hydrogen sulfide or hydrogen sulfide - H 2 S. A gas that is colorless and has a sweet taste. The smell is sharp, extremely unpleasant, resembles a rotten egg. Poisonous, inhibits the respiratory center, as it binds copper ions. Therefore, when they are poisoned, suffocation and death occur. It is widely used in medicine, organic synthesis, sulfuric acid production, as well as energy-efficient raw materials.
- Sulphides of metals are widely used in medicine, in sulfuric acid production, inks, in the manufacture of phosphors and other places. The general formula is Me x S y .
Compounds with oxidation state +4
Sulfur compounds 4 are primarily oxide and its corresponding salts and acid. All of them are fairly common compounds that have a certain value in industry. They can also act as oxidizing agents, but more often exhibit reducing properties.
The sulfur compounds with an oxidation state of +4 are as follows:
- oxide - sulfur dioxide gas SO 2 ;
- acid - sulphurous H 2 SO 3 ;
- salts have the general formula Me x (SO 3 ) y.
One of the most common is sulfur dioxide, or anhydride. It is a colorless substance with the smell of a burnt match. In large clusters, it is formed during the eruption of volcanoes; at this moment it is easy to determine by smell.
It dissolves in water with the formation of easily decomposing acid - sulphurous. It behaves like a typical acid oxide, forms salts, which are included in the form of sulfite ion SO 3 2- . This anhydride is the main gas that affects air pollution. It affects the formation of acid rain. It is used in industry in sulfuric production.
Compounds in which sulfur has an oxidation state of +6
These include, first of all, sulfuric anhydride and sulfuric acid with its salts:
Since the sulfur atom in them is in the highest oxidation state, the properties of these compounds are quite explainable. They are strong oxidizing agents.
Sulfur oxide (VI) - sulfuric anhydride - is a volatile, colorless liquid. A characteristic feature is a strong moisture-absorbing ability. It smokes outdoors. When dissolved in water, it gives one of the strongest mineral acids - sulfuric. Its concentrated solution is a heavy, oily, slightly yellowish liquid. If the anhydride is dissolved in sulfuric acid, you get a special compound called oleum. It is used in industry for the production of acid.
Among salts - sulfates - compounds such as:
- gypsum CaSO 4 · 2H 2 O;
- Barite BaSO 4 ;
- mirabilite;
- lead sulfate and others.
They find application in construction, chemical synthesis, medicine, the manufacture of optical instruments and glasses, and even the food industry.
Hydrosulphates are widely used in metallurgy, where they are used as flux. And also they help to convert many complex oxides into soluble sulfate forms, which is used in the corresponding industries.
Studying sulfur in a school chemistry course
When is the best time for students to learn about what sulfur is, what are its properties, what is a sulfur compound? Grade 9 is the best period. This is not the very beginning when for children everything is new and incomprehensible. This is the middle of the study of chemical science, when the foundations laid earlier will help to fully understand the topic. Therefore, it is precisely the second half of the graduation class that stands out for consideration of these issues. Moreover, the whole topic is divided into several blocks, in which the lesson "Sulfur Compounds. Grade 9" is a separate lesson.
This is due to their abundance. The issue of sulfuric acid production in industry is also separately considered. In general, an average of 3 hours is devoted to this topic.
But organic sulfur compounds are submitted for study only in the 10th grade, when organic matters are considered. They are also affected by biology in high school. After all, sulfur is part of such organic molecules as:
- thioalcohols (thiols);
- proteins (tertiary structure on which the formation of disulfide bridges occurs);
- thioaldehydes;
- thiophenols;
- thioethers;
- sulfonic acids;
- sulfoxides and others.
They are isolated in a special group of organosulfur compounds. They are important not only in the biological processes of living things, but also in industry. For example, sulfonic acids are the basis of many drugs (aspirin, sulfanilamide or streptocide).
In addition, sulfur is a constant component of compounds such as some:
- amino acids;
- enzymes;
- vitamins;
- hormones.