All inorganic substances are divided into simple compounds: metals; non-metals. And complex: binary compounds; grounds; acids; salt.
How are non-metals located in the periodic table? Of the 118 currently known chemical elements, 96 are metals, and only 22 are non-metals by the general characteristics of the elements. Non-metallic chemical elements account for most of the mass of living organisms. And the composition of the earth's atmosphere includes both simple and complex substances formed by non-metal elements.
The location of non-metallic elements in the Periodic system
In the short-period variant, non-metals are in the main subgroups. We will consider the general characteristic below. Non-metals are located to the right and above the diagonal of Bohr and Astat. In the long-period variant - at the end on the right in groups IVA, VA, VIA, VIIA, VIIIA.
Of all the chemical elements discovered to date, non-metallic elements are few - only 22. Of these, 16 are active elements and 6 are inert gases. However, the chemistry of non-metals is richer than the chemistry of all metals. Non-metallic elements play a huge role in the existence of life on Earth.
General characteristics of non-metals
Atoms of non-metallic elements at the external level contain from four to seven electrons and eight electrons in inert gases, with the exception of hydrogen (one electron) and helium (2 electrons). Therefore, in the general characteristic of the structure of non - metal atoms is the ability to both receive and give up electrons, playing the role of both oxidizing agents and reducing agents.
Thus, non-metallic elements in compounds exhibit both negative and positive oxidation states. The characteristic values of the valency and oxidation state of non-metals are related to the structure of their external electronic level
So, for example, sulfur can exhibit a valency of 2, 4, 6 due to the separation of electrons. In nature, non-metals, in addition to oxygen, nitrogen, hydrogen, sulfur and inert gases, exist in the form of compounds: sulfides, oxides, chlorides, silicates, sulfates, carbonates, phosphates of various metals.
Non-metallic elements in free form exist in the form of simple substances - non-metals. Consider their structure, properties and application. Non-metal atoms are linked together by a covalent bond. The forms of existence of non-metals are different. Hydrogen, iodine, chlorine, fluorine, bromine, exist only in the form of diatomic molecules H2, I2, Cl2, F2 Br2. The reason is that they have only one opportunity to form a common pair due to a single unpaired electron.
Allotropy of non-metals
With an increase in the number of unpaired electrons for elements, it becomes possible to form simple substances of different compositions - allotropic modifications. So, oxygen forms two allotropic modifications.
Hydrogen H2, fluorine F2, chlorine Cl2, nitrogen N2, oxygen O2, ozone O3 are fairly light non-polar molecules that interact weakly with each other. Therefore, all of the listed substances are gases at ordinary temperature.
Bromine Br2 is a liquid, and I2 is a solid. In solid form, they all have a molecular crystal lattice.
Production Methods
The first paragraph of the general characteristics of non-metals can be considered methods for their preparation. Non-metals are obtained in various ways:
- Separation from other substances from natural compounds. For example, the separation of liquid air into oxygen, nitrogen, and residual inert gases.
- Reduction from a compound if non-metal in it has a positive oxidation state. For example, the reduction of hydrogen from water by electrolysis: +1 –2 0 Cathode (-) 2H2O + 2 = H2 + 2OH - .
- Oxidation from a compound in which non-metal has a negative oxidation state. For example, the oxidation of chloride ions during the electrolysis of a solution or molten sodium chloride: Anode (+) 2Cl - - 2 = Cl 0 2 ↑.
Also distinguish industrial and laboratory methods for producing non-metals.
Physical properties
The second point of the general characteristic of non-metals is their physical properties. Basically, non-metals have an atomic or molecular crystal lattice. Some of them conduct electric current well, or are semiconductors. The third point in the study of the general characteristics of non-metals is to consider their chemical properties.
Non-metals can serve in chemical reactions as oxidizing agents and reducing agents. The exception is fluorine F2, which always plays the role of an oxidizing agent. Therefore, all reactions involving non-metals are redox.
Consider the ratio of non-metals to water, metals, to each other, as well as to oxides, acids, bases and salts. All non-metals are resistant to heat, so most of their reactions occur only at high temperatures:
1. Under normal conditions, only fluorine actively interacts with water: F2 + H2O = 2HF + O 2O = O2; O2 + O = O3. We can say that water burns in fluorine. In this case, a complex mixture of substances is formed, including oxygen fluorides OF2 and O2F2. Chlorine and bromine interact with water only partially: Cl2 + H2O ← → HCl + HClO Chlorine solutions of Cl2 in water are called chlorine water. When water vapor is passed over heated coal, water gas is formed: C + H2O = t o CO + H2.
2. All non-metals, except inert gases, interact with metals. As a result, binary compounds are formed: oxides, hydrides, carbides, nitrides, phosphides, sulfides, chlorides, bromides, iodides, etc. Ca + H2 = CaH2 - calcium hydride.
3. Non-metals react with each other only when heated (except for fluorine), forming binary compounds of various types:
- Oxides: N2 + O2 ← → 2NO – Q - nitric oxide (II) Of non-metals, only chlorine, bromine, iodine do not directly react with oxygen. Their oxides are obtained indirectly.
- Hydrogen compounds: H2 + S = H2S - hydrogen sulfide.
4. Under normal conditions, non-metals practically do not react with oxides. When heated, a few, but practically important reactions occur. For example, the reduction of metals and nonmetals from oxides: FeO + C = Fe + CO ↑.
Consider the general characteristic of non-metals on the example of halogens
Fluorine F2 and chlorine Cl2 exhibit similar physical properties: they are poisonous gases with a pungent odor, with fluorine having a light yellow color and chlorine having a yellow-green color. Br2 bromine is a heavy reddish-brown liquid. Chlorine and bromine are partially soluble in water; their solution is called chlorine and bromine water.
Iodine I2 - very slightly soluble in water, better soluble in alcohol or other organic solvents.
Halogens are obtained by electrolysis of a melt or NaCl solution or by displacement with chlorine. Halogens displace each other from solutions of their acids: 2HBr + Cl2 = 2HCl + Br2.