In the periodic table, non-metals are located in the upper right triangle, and when the group number decreases, their number in it also decreases. In the seventh group (halogens), all elements are non - metals. These are fluorine, chlorine, bromine, iodine and astatine. Although we do not consider the latter, since, firstly, it is radioactive by itself, it is found in the earth's crust only in the form of an intermediate decay product of uranium, and its compound HAt (astatine hydrogen) obtained in the laboratory is extremely unstable and behaves in solution not like other hydrogen halides. The sixth group of non-metals is already smaller (oxygen, sulfur, selenium and tellurium, which is a metalloid), in the fifth there are three (nitrogen, phosphorus and arsenic), in the fourth - two (carbon and silicon), and in the third lonely boron. Hydrogen compounds of non-metals of the same group have similar chemical properties.
Halogens
Hydrogen halides are the most important halogen compounds. By their properties, these are oxygen-free acids that dissociate in water into a halogen anion and a hydrogen cation. All are highly soluble. The chemical bond between the atoms in the molecule is covalent, the electron pair is biased toward the halogen as being more electronegative. Since the higher the periodic table, the greater the electronegativity of the atom, with a decrease in the period, the covalent bond becomes more and more polar. Hydrogen carries a greater partial positive charge, in the solution it is easier to detach from the halogen, that is, the compound dissociates more fully and more successfully, and the strength of acids increases in the series from iodine to chlorine. We did not say about fluorine, because in its case the exact opposite is observed: hydrofluoric (hydrofluoric acid) is weak and dissociates very poorly in solutions. This is explained by such a phenomenon as hydrogen bonds: hydrogen is introduced into the electron shell of the fluorine atom of a “foreign” molecule, and an intermolecular bond arises that does not allow the compound to dissociate as expected.
This is clearly confirmed by the graph with boiling points of various hydrogen compounds of non-metals: from them the compounds of elements of the first period — nitrogen, oxygen, and fluorine — having hydrogen bonds stand out.
Oxygen group
The hydrogen compound of oxygen is, obviously, water. There is nothing remarkable to say about it, except that the oxygen in this compound, unlike sulfur, selenium and tellurium in similar compounds, is in sp 3 hybridization - this is indicated by the valence angle between two bonds with hydrogen. It is assumed that for the remaining elements of group 6 this is not observed due to the large difference in the energy characteristics of the external levels (for hydrogen 1s, for oxygen - 2s, 2p, while for the others 3, 4 and 5, respectively).
Hydrogen sulfide is released during rotting of a protein; therefore, it is manifested by the smell of rotten eggs and is poisonous. It is found in nature in the form of volcanic gas and is released by living organisms in the processes already mentioned (decay). Used in chemistry as a strong reducing agent. During the eruption of volcanoes, mixing with sulfur dioxide, forms volcanic sulfur.
Hydrogen selenium and hydrogen telluride are also gases. Terribly poisonous and have an even more disgusting smell than hydrogen sulfide. As the period increases, the reducing properties increase, and the strength of aqueous solutions of acids also.
Nitrogen group
Ammonia is one of the most famous non-metal hydrogen compounds. Nitrogen here is also in sp 3 hybridization, keeping with it one lone electron pair, due to which it then forms various ionic compounds. It has a fairly strong reducing properties. It is known for its good ability (due to the same lone electron pair) to form complexes, acting as a ligand. Known ammonia complexes of copper, zinc, iron, cobalt, nickel, silver, gold and much more.
Phosphine - a hydrogen compound of phosphorus - has even stronger reducing properties. Extremely toxic, self-igniting in the air. Has a dimer present in the mixture in small quantities.
Arsine is arsenic hydrogen. Toxic, like all arsenic compounds. It has a characteristic garlic odor that appears due to the oxidation of part of the substance.
Carbon and silicon
Methane - a hydrogen compound of carbon - is the starting point on the boundless space of organic chemistry. This is exactly what happened with carbon, because it can form long stable chains with carbon-carbon bonds. In the framework of this article, it is worth saying that the carbon atom also has sp 3 hybridization here. The main reaction of methane is burning, during which a large amount of heat is released, which is why methane (natural gas) is used as fuel.
Silane is a similar silicon compound. It spontaneously ignites in the air and burns out. It is noteworthy that it is also capable of forming chains similar to carbon: known, for example, disilane and trisilane. The problem is that the silicon-silicon bond is much less stable, and the chains are easily broken.
Boron
With boron, everything is very interesting. The fact is that its simplest hydrogen compound, borane, is unstable and dimerizes, forming diborane. Diborane spontaneously ignites in air, but is stable in itself, as well as some subsequent boranes containing up to 20 boron atoms in a chain - in this they advanced farther than silanes with a maximum number of 8 atoms. All boranes are poisonous, including those possessing the properties of nerve agents.
The molecular formulas of hydrogen compounds of non-metals and metals are written in the same way, but they differ in structure: metal hydrides have an ionic structure, non-metals have a covalent structure.