Examples of Hydrides
We explain that what are some examples of Hydrides? The hydrides are chemical compounds that are formed when hydrogen atoms are attached to a metal or metalloid. The metals always act with a positive valence , as delivered their valence electrons. The same thing usually happens with hydrogen. However, when forming a hydride it participates with a negative valence –1 and receives the electron from the metal until the stable molecule is created. examples of hydrides
In hydrides of a metallic nature, properties such as electrical and thermal conductivities predominate. These are those that are made up of transition metals. On the other hand, there are saline hydrides which in their natural state are poor conductors and are more brittle. The latter, however, can dissolve in water and release their ions more easily, promoting conductivity in aqueous solution. The latter carry metals of groups IA and IIA.The hydrides of alkali (group IA), alkaline earth (group IIA) and earth (group IIIA) elements behave as binary salts, that is, as chlorides, bromides and iodides. Their bonds are generally brittle and can be broken when immersed in water (by hydrolysis). When the hydride molecules M – H are immersed in those of water H – OH , the immediate reaction will be the release of hydrogen gas (H – H or H 2 ) and the formation of metal hydroxide (M – OH) .
Properties of hydrides examples of hydrides
The properties of hydrides vary depending on the type of hydride: ionic, molecular or metallic, so their properties must be noted separately.
Ionic or saline hydrides examples of hydrides
They are crystalline white solids, but due to the presence of impurities they acquire a grayish color. These hydrides are not soluble in common solvents, such as water, alcohol, etc. They also have high boiling and melting points.
They have a high density and in the molten state they can conduct electricity. examples of hydrides
Ionic hydrides are considered basic or alkaline in nature, since dissolved in water they form hydroxides and release molecular hydrogen:
The reaction of ionic hydride with water is very vigorous and dangerous: it produces hydrogen in gaseous form, which is a combustible and flammable material.
Ionic hydrides can also react with metal halides, made up of a metal and a non-metal known as halogen (MX, X = F, Cl, Br, I):
4 LiH + AlCl 3 → LiAlH 4 + 3 LiCl
LiH (lithium hydride) is a binary compound; while LiAlH 4 (lithium aluminum hydride) is a ternary compound, that is, it is made up of three chemical elements. examples of hydrides
Molecular or covalent hydrides examples of hydrides
They are in a liquid or gaseous state, unlike ionic hydrides, which are solid. They have low boiling and melting points, it being observed that as the molecular weight of the hydride increases, the boiling point increases ; With the exception of ammonia (NH 3 ), water (H 2 O) and fluorine hydride (HF).
Covalent hydrides are poor conductors of electricity and many of their properties are due to the formation of hydrogen bonds. Covalent hydrides are considered acids, since dissolved in water they can originate acids, for example, hydrochloric acid.
Metal hydrides examples of hydrides
They are in a solid state , presenting the dark tone of metals. They are good conductors of electricity and have glossy surfaces. Metal hydrides that are stable in air become reactive when heated, for example uranium hydride (UH 3 ) exhibits this property.
Nomenclature of hydrides examples of hydrides
Hydrides can be named in a simple way by following these steps:
- The words “hydride of” are written.
- The name of the metal is written.
- If the metal has two or more valences, it is written in Roman numerals. examples of hydrides
The way to name the hydrides is simple, and does not vary much in any of the nomenclatures. If the metal or non-metallic element has more than one valence, this is specified in parentheses and with a Roman numeral according to the stock nomenclature.
For example, FeH 3 is called iron (III) hydride , and CoH 2 cobalt (II) hydride. These same hydrides can also be named using systematic nomenclature, which makes use of the Greek numerator prefixes (di, tri, tetra, etc.). Thus, FeH 3 is called iron trihydride, and CoH 2 cobalt dihydride.
The classical nomenclature is not widely used for hydrides. For example, NaH is better known as sodium hydride, not sodium hydride.
How are hydrides formed?
Ionic or saline hydrides
They are formed by the reaction of hydrogen with a metal belonging to the group of alkali metals or to the group of alkaline-earth metals.
In hydrides formed with these metals, hydrogen is in the H – form , known as the hydride anion.
The alkali metals (lithium, sodium, potassium, rubidium, and cesium) react with hydrogen to form their corresponding hydrides:
2 M (l) + H 2 (g) → 2MH (s)
The metal M when reacting is in the liquid state, and the hydrogen in the gaseous state , so the reaction requires high temperatures and high pressures. Consider the following example:
2 Li (l) + H 2 (g) → 2 LiH (s)
The reaction of hydrogen with alkaline earth metals (beryllium, magnesium, calcium, strontium and barium), for the formation of hydrides, is similar to that observed with alkali metals.
Magnesium and beryllium form hydrides, but their bonds with hydrogen are of the covalent type; that is, non-ionic, unlike the other alkaline earth metals:
Ca (l) + H 2 (g) → CaH 2 (s)
Molecular hydrides
Hydrogen can react with nonmetals, corresponding to groups 14, 15, 16 and 17 of the Periodic Table, to form molecular hydrides. Consider, for example, the formation of fluorine hydride by direct blending or mixing of hydrogen with fluorine:
H 2 (g) + F 2 (g) → 2 HF (g)
HF is better known as hydrogen fluoride, but it is also called fluorine hydride.
Likewise, hydrogen can react with oxygen (group 16 of the Periodic Table) following the same scheme:
2 H 2 (g) + O 2 (g) → 2 H 2 O (g)
The reaction requires a supply of heat to produce hydrogen oxide (water) or oxygen hydride.
Likewise, hydrogen can react with nitrogen, belonging to group 15 of the Periodic Table to form nitrogen hydride, better known as ammonia (NH 3 ).
N 2 (g) + 3 H 2 (g) → 2 NH 3 (g)
The reaction requires the supply of heat, high pressure and the presence of catalysts (they accelerate chemical reactions).
Metal hydrides
They are formed by the reaction of transition metals (groups 3, 4, 5, 6, 10, 11 and 12 of the Periodic Table) with hydrogen. However, the transition metals of groups 7, 8 and 9 do not form compounds with hydrogen, a phenomenon known as the hydride gap or hydride gap.
A unique characteristic of transitional metal hydrides is that they do not always have a fixed ratio between the number of hydrogen atoms and the number of atoms present in the hydride. That is, its formulas and structures are not simple to represent.
Uses or Applications of hydrides
Hydrides are present in nickel metal hydride (NiMH) batteries, used in conjunction with rare earth metals, cobalt, or manganese. Various metal hydrides have been examined for use in electric cars powered by hydrogen-related fuel cells.
Reducing agents
Lithium hydride and sodium borohydride (NaBH 4 ) are used as chemical reducing agents in organic synthesis reactions.
Hydrogen storage and other related uses
There are pilot tests of the use of hydrogen as a fuel in motor vehicles, but due to its explosiveness its use as a fuel has been limited. The use of hydrides has been proposed as a form of hydrogen storage, in order to control its danger.
In addition, hydrides have been used for the purification and separation of hydrogen and in temperature sensors.
Desiccants
Calcium hydride is used to remove the water present in organic solvents.
Acids originating from molecular hydrides
For example: hydrochloric acid is formed by the dissolution in an aqueous medium of chlorine hydride (HCl), using hydrochloric acid in the elimination of the oxides that cover the iron, the acidification of oil wells, the production of chloride of calcium and mineral treatment. examples of hydrides
Fertilizers
Ammonia (NH 3 ) is a hydride that is used as a liquid fertilizer and is used for the synthesis of compounds with ammonium nitrate and ammonium sulfate, which are used as fertilizers.
Water
It is the most important hydride. It is used in many industries with different uses and applications. Water is the main responsible for the existence of living beings.
30 Examples of hydrides
- Lithium hydride LiH
- Sodium hydride NaH
- Potassium hydride KH
- Rubidium hydride RbH
- Cesium hydride CsH
- Francium hydride FrH
- Beryllium hydride BeH 2
- Magnesium hydride MgH 2
- Calcium hydride CaH 2
- Strontium hydride SrH 2
- Barium hydride BaH 2
- Radium hydride RaH 2
- Boron hydride or borane BH 3
- Aluminum hydride AlH 3
- Gallium hydride GaH 3
- Indium hydride InH 3
- Thallium hydride TlH 3
- Iron II Hydride FeH 2
- Iron III hydride FeH 3
- Zinc hydride ZnH 2
- Carbon hydride or methane CH 4
- Silicon hydride SiH 4
- Germanium hydride GeH 4
- Tin II Hydride SnH 2
- Tin hydride IV SnH 4
- Lead II Hydride PbH 2
- Lead IV Hydride PbH 4
- Titanium hydride TiH 4
- Copper hydride I CuH
- Copper II hydride CuH 2
Finally, other examples of hydrides will be listed with their respective formulas and names: examples of hydrides
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SnH4: tin hydride |
PH3: phosphorous hydride (phosphine) or phosphorous trihydride |
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KH: lead hydride |
MgH2: magnesium hydride or magnesium dihydride |
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KH: potassium hydride |
CH4: carbon hydride or carbon tetrahydride (methane) |
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CaH2: calcium hydride |
FeH2: iron (II) hydride |
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NaH: sodium hydride |
ZnH2: zinc hydride |
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LiH: lithium hydride |
BaH2: barium hydride |
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CsH: cesium hydride |
BH3: boron hydride (borane) |
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BeH2: beryllium hydride or beryllium dihydride |
SiH4: silicon hydride (silane) |