Sulfur (Latin Sulfur) is a non-metal element. The chemical symbol S, the ordinal number in the periodic table - 16. The valency of sulfur was established even before the study of the structure of the atom. Determined its value on the basis of the property to replace, attract or attach a number of other atoms or groups. Later, researchers found out the role of negatively charged particles (electrons) in the origin of the chemical bond.
Valence of sulfur: which features of atoms affect its significance?
By the prevalence on Earth, the chemical element is on the 16th place. It occurs in the form of bright yellow crystals or powder in rocks, near active and extinct volcanoes. The most famous natural compounds are sulphides and sulfates.
Features of the element and substance:
- Strong non-metal.
- By electronegativity (EO) or the ability to attract electrons to itself, sulfur is second only to fluorine, oxygen, nitrogen, chlorine and bromine.
- Interacts with metals and non-metals, simple and complex substances.
Differences in properties depend on the structure and state of the atom, the difference in the values of EO. Let us find out what valence can be present in sulfur in compounds. Their chemical behavior depends on the structure of the energy shells, the number and location of external electrons in the atom.
Why is the valence different?
Stable natural isotopes of sulfur with mass numbers 32 (the most common), 33, 34 and 36 are stable. The atom of each of these nuclides contains 16 positively charged protons. In the space near the nucleus 16 electrons move with a huge speed. They are infinitesimally small, negatively charged. Less than 6 external particles are attracted to the nucleus (more free). Several of them or all take part in the formation of different types of chemical bonds. According to modern concepts, the valence of sulfur is determined by the number of created common (binding) electron pairs. Usually, in drawings and diagrams, the outer particles participating in this process are represented by dots around the chemical sign.
How does the valence depend on the structure of the atom?
Using the energy diagram, it is possible to show the structure of levels and sublevels (s, p, d) on which the valence formula of sulfur depends. Two differently directed arrows symbolize paired, one - unpaired electrons. The outer space of the sulfur atom forms the orbitals of 6 particles, but 8 is necessary for stability according to the rule of the octet. The configuration of the valence shell reflects the formula 3s23p4. The electrons of the incomplete layer have a large energy reserve, which causes the unstable state of the entire atom. To achieve stability, the sulfur atom requires two additional negative particles. They can be obtained by forming covalent bonds with other elements or by absorbing two free electrons. In this case, sulfur exhibits a valence II (-). The same value can be obtained using the formula: 8 - 6 = 2, where 6 is the group number in which the element is located.
Where are the compounds in which the valence of sulfur is II (-)?
The element attracts or completely removes electrons from atoms with a lower electronegativity value on the Polling scale. Valence II (-) is manifested in the sulphides of metals and non-metals. An extensive group of such compounds is found in rocks and minerals of great practical importance. These include pyrite (FeS), sphalerite (ZnS), galena (PbS), and other substances. Crystals of iron sulphide have a beautiful yellowish-brown color and shine. Often the mineral of pyrite is called "gold of fools". To obtain metals from ores, they are fired or regenerated. Hydrogen sulfide H2S has the same electronic structure as water. H2S Origin:
- Is released when decaying proteins (eg, a hen's egg);
- Erupts with volcanic gases;
- Accumulates in natural waters, oil;
- Is emitted into voids in the earth's crust.
Why is the formula of oxide of tetravalent sulfur SO2?
The dioxide formula shows that one sulfur atom in a molecule is bound to two oxygen atoms, each of which requires 2 electrons to an octet. The resulting bond is by nature covalent polar (EO of oxygen is greater). The valence of sulfur in this compound has the value IV (+), because 4 electrons of the sulfur atom are displaced towards two oxygen atoms. The formula can be written as follows: S2O4, but by the rules it is necessary to reduce by 2. Dioxide, when dissolved in water, forms ions of weak sulfuric acid. Its salts - sulfites - are strong reducing agents. SO2 gas serves as an intermediate in the production of sulfuric acid.
In what substances does sulfur show its highest valence?
SO3 oxide or S2O6 is a colorless liquid, at temperatures below 17 ° C it hardens. In the SO3 compound, the oxygen valence is II (-), and sulfur VI (+). The higher oxide dissolves in water and forms a strong dibasic sulfuric acid. For a greater role in production processes, the substance was called "bread of the chemical industry". An important role in the economy and medicine belongs to acid salts - sulfates. Crystalline hydrate of calcium (gypsum), sodium (Glauber's salt), magnesium (English or bitter salt) are used.
In the formation of different types of chemical bond, 1, 2, 3, 4, 6 external electrons can participate. We call the possible valencies of sulfur, taking into account that there are rare and unstable compounds: I (-), II (-), II (+), III (+), IV (+), VI (+). The second positive valence element is obtained in SO monoxide. The most common values of II (-), IV (+), VI (+) show sulfur in a group of substances having industrial, agricultural and medical significance. Its connections are used in the production of fireworks.
The big problem is the trapping of waste gases, among which sulfur oxides IV (+), VI (+) and hydrogen sulfide harmful to man and the environment. Technologies have been developed for processing these gaseous wastes and obtaining sulfuric acid and sulfates from them. To this end, chemical plants are built near metallurgical plants or in one area. As a result, the volume of contaminants is reduced, less "sulfuric acid rain" occurs.