Sulfur (lat. Sulfur) - a non-metal element. The chemical symbol S, the serial number in the periodic table is 16. The valency of sulfur was established even before studying the structure of the atom. We determined its value on the basis of the property to replace, attract, or attach a certain number of other atoms or groups. Researchers later found out the role of negatively charged particles (electrons) in the occurrence of a chemical bond.
Sulfur valency: what features of atoms affect its value?
In terms of prevalence on Earth, the chemical element is in 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 sulfides 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.
- It 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 valency can be 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 valence different?
Natural sulfur isotopes 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 space near the nucleus, 16 electrons move at a tremendous speed. They are infinitesimal, negatively charged. Less attracted to the core (more free) 6 external particles. Several or all of them are involved 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. Typically, in the figures and diagrams, the external particles participating in this process are represented by dots around a chemical sign.
How does valency depend on the structure of the atom?
Using the energy diagram, you can show the structure of levels and sublevels (s, p, d), on which the sulfur valency formula depends. Two oppositely directed arrows symbolize paired, one - unpaired electrons. The outer space of the sulfur atom is formed by the orbitals of 6 particles, and 8 is necessary for stability according to the octet rule. The valence shell configuration is reflected in the formula 3s23p4. The electrons of the incomplete layer have a large energy reserve, which causes an unstable state of the entire atom. To achieve stability, the sulfur atom requires two additional negative particles. They can be obtained by the formation of
covalent bonds with other elements or by absorption of two free electrons. In this case, sulfur exhibits a valency of II (-). The same value can be obtained using the formula: 8 - 6 = 2, where 6 is the number of the group in which the element is located.
Where are compounds in which the valency of sulfur is II (-)?
An element attracts or completely removes electrons from atoms with a lower electronegativity on the Polling scale. Valence II (-) is manifested in sulfides of metals and nonmetals. 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. Iron sulfide crystals have a beautiful tan color and luster. Often the mineral pyrite is called the "gold of fools." To obtain metals from ores, they are fired or reduced. H2S hydrogen sulfide has the same electronic structure as water. Origin of H2S:
- secreted by the decay of proteins (for example, chicken eggs);
- erupts with volcanic gases;
- accumulates in natural waters, oil;
- stands out in the void in the earth's crust.
Why is the formula of tetravalent sulfur oxide SO2?
The dioxide formula shows that one sulfur atom in a molecule is bound to two oxygen atoms, each of which needs 2 electrons per octet. The resulting bond is covalent polar in nature (EO of oxygen is greater). The valence of sulfur in this compound is IV (+), because 4 electrons of the sulfur atom are shifted towards two oxygen atoms. The formula can be written as follows: S2O4, but according to the rules it is necessary to reduce by 2. The dioxide, when dissolved in water, forms weak sulfuric acid ions. Its salts, sulfites, are powerful reducing agents. SO2 gas serves as an intermediate in the
production of sulfuric acid.In which substances does sulfur exhibit its highest valency?
SO3 or S2O6 oxide is a colorless liquid; it hardens at temperatures below 17 ° C. In the SO3 compound, the oxygen valency is II (-), and the sulfur is VI (+).
The higher oxide dissolves in water and forms strong dibasic sulfuric acid. For a large 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 (Epsom or bitter salt) are used.
1, 2, 3, 4, 6 external electrons can participate in the formation of different types of chemical bonds. We will call the possible valencies of sulfur, given that there are rare and unstable compounds: I (-), II (-), II (+), III (+), IV (+), VI (+). The element acquires the second positive valency in SO monoxide. The most common values of II (-), IV (+), VI (+) are sulfur in the group of substances of industrial, agricultural and medical importance. Its compounds are used in the manufacture of fireworks.
The big problem remains the capture of exhaust gases, among which are harmful to humans and the environment sulfur oxides IV (+), VI (+) and hydrogen sulfide. Technologies have been created for the processing of these gaseous wastes and the production of sulfuric acid and sulfates from them. To this end, chemical plants are being built next to metallurgical plants or in the same area. As a result, the amount of pollution is reduced, less "sulfuric acid rains."