- Properties of inorganic compounds
- Variable combinations of elements
- Low molecular or formula masses
- They are usually solid or liquid
- Very high melting and boiling points
- Present colors
- They have various oxidation states
- Types of inorganic compounds
- Oxides
- Sulfides
- Halides
- Hydrides
- Nitrides
- Phosphides
- Carbides
- Carbonates and cyanides
- Examples
- References
The inorganic compounds are those lacking a proper carbon backbone; that is, they do not have both CC or CH bonds at the same time. In terms of chemical variety, they comprise almost the entire periodic table. Metals and non-metals combine, covalently or ionically, to define what is known as inorganic chemistry.
Inorganic compounds sometimes differ markedly when compared to organic compounds. For example, it is said that inorganic compounds cannot be synthesized by living organisms, while organic ones can.
Amethyst crystals, as well as other minerals, rocks, and stones, are examples of inorganic compounds enriching the earth's crust. Source: Pexels.
However, bones, oxygen produced by plants, carbon dioxide that we exhale, hydrochloric acid from gastric juice, and methane released by certain microorganisms show that indeed some inorganic compounds can be synthesized in biological matrices.
On the other hand, inorganic compounds are thought to be more abundant in the Earth's crust, mantle, and core in mineral body forms. However, this criterion is not enough to pigeonhole its properties and characteristics.
Thus, the line or border between the inorganic and organic is partially defined by the metals and the absence of the carbon skeleton; without mentioning the organometallic compounds.
Properties of inorganic compounds
Although there is not as such a series of properties that are fulfilled for all inorganic compounds, there are certain generalities observed in a decent number of them. Some of these properties will be mentioned below.
Variable combinations of elements
Inorganic compounds can be formed by any of the following combinations: metal-nonmetal, nonmetal-nonmetal, or metal-metal. Non-metallic elements can be replaced by metalloids and inorganic compounds will also be obtained. Therefore, the possible combinations or bonds are highly variable as many chemical elements are available.
Low molecular or formula masses
Inorganic molecules, like the formulas of their compounds, tend to have little mass compared to organic compounds. This is the case except when it comes to inorganic polymers, which have non-metal-non-metal (SS) covalent bonds.
They are usually solid or liquid
The way in which the elements interact in an inorganic compound (ionic, covalent or metallic bonds) allows their atoms, molecules or structural units to define liquid or solid phases. Therefore, many of them are solid or liquid.
This does not mean, however, that there are not a considerable amount of inorganic gases, but that their number is less than that of their respective solids and liquids.
Very high melting and boiling points
Inorganic solids and liquids are often characterized by very high melting and boiling points, respectively. Salts and oxides demonstrate this generality, as they require high temperatures to melt, and even more to boil.
Present colors
Although there are several exceptions to this property, the colors observed in inorganic compounds are due, for the most part, to transition metal cations and their electronic d - d transitions. For example, chromium salts are synonymous with attractive colors, and copper, blue-green hues.
They have various oxidation states
As there are so many ways to link and a wide number of possible combinations between the elements, they can adopt more than one number or oxidation state.
For example, chromium oxides: CrO (Cr 2+ O 2-), Cr 2 O 3 (Cr 2 3+ O 3 2-) and CrO 3 (Cr 6+ O 3 2-) demonstrate how chromium and oxygen modify their oxidation states to generate different oxides; some more ionic, and others more covalent (or oxidized).
Types of inorganic compounds
The types of inorganic compounds are defined essentially by non-metallic elements. Why? Although metals are more abundant, not all of them combine to give mixed crystals like those of alloys; while the less abundant nonmetals are chemically versatile in terms of bonds and interactions.
A nonmetal, in its ionic form or not, combines with almost all the metals in the periodic table, regardless of their oxidation state. That is why some of the types of inorganic compounds will be mentioned based on the non-metallic elements.
Oxides
In oxides, the existence of the anion O 2- is assumed, and its generic formula is M 2 O n, where n is the number or oxidation state of the metal. However, even solids where there are MO covalent bonds are called oxides, which are many; for example, the oxides of the transition metals have a high covalent character in their bonds.
When the formula of a hypothetical oxide does not agree with M 2 O n, then you have a peroxide (O 2 2-) or a superoxide (O 2 -).
Sulfides
In sulfides, the existence of the anion S 2- is assumed and its formula is identical to that of the oxide (M 2 S n).
Halides
In halides we have the anion X -, where X is any of the halogens (F, Cl, Br and I), and its formula is MX n. Some of the metal halides are ionic, saline and soluble in water.
Hydrides
In hydrides we have the anion H - or the cation H +, and their formulas vary if they are formed by a metal or a nonmetal. Like all types of inorganic compounds, there can be MH covalent bonds.
Nitrides
In nitrides, the existence of the anion N 3- is assumed, its formula is M 3 N n, and they cover a wide range of ionic, covalent, interstitial compounds or three-dimensional networks.
Phosphides
In phosphides, the existence of the anion P 3- is assumed and its cases are similar to that of nitrides (M 3 P n).
Carbides
In carbides the existence of C 4-, C 2 2- or C 3 4- anions is assumed, with partially covalent MC bonds in some compounds.
Carbonates and cyanides
These anions, CO 3 2- and CN -, respectively, are a clear example that in inorganic compounds there can be purely covalent carbon atoms. In addition to carbonates, there are sulfates, chlorates, nitrates, periodates, etc.; that is, families of oxysalts or oxoacid salts.
Examples
Finally, mention will be made of some inorganic compounds accompanied by their respective formulas:
-Lithium hydride, LiH
Structure of lithium hydride
-Lead nitrate, Pb (NO 3) 2
-Carbon dioxide, CO 2
-Barium peroxide, BaO 2
Crystal structure of BaO2
-Aluminum chloride, AlCl 3
-Titanium tetrachloride, TiCl 4
-Nickel (II) sulfide, NiS
-Nitrogen or ammonia trihydride, NH 3
-Hydrogen oxide or water, H 2 O
-Tungsten carbide, WC
-Calcium phosphide, Ca 3 P 2
-Sodium nitride, Na 3 N
-Copper (II) carbonate, CuCO 3
-Potassium cyanide, KCN
-Hydrogen iodide, HI
-Magnesium hydroxide, Mg (OH) 2
-Iron (III) oxide, Fe 2 O 3
References
- Shiver & Atkins. (2008). Inorganic chemistry. (Fourth edition). Mc Graw Hill.
- Wikipedia. (2019). Inorganic compound. Recovered from: en.wikipedia.org
- Elsevier BV (2019). Inorganic Compound. ScienceDirect. Recovered from: sciencedirect.com
- Marauo Davis. (2019). What Are Inorganic Compounds? - Definition, Characteristics & Examples. Study. Recovered from: study.com
- Chemistry LibreTexts. (September 18, 2019). Names and Formulas of Inorganic Compounds. Recovered from: chem.libretexts.org