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Source: Wikipedia, the free encyclopedia.
Pure water (H2O) is an example of a compound. The ball-and-stick model of the molecule shows the spatial association of two parts hydrogen (white) and one part(s) oxygen (red)

A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) composed of atoms from more than one element held together by chemical bonds. A molecule consisting of atoms of only one element is therefore not a compound.

There are four types of compounds, depending on how the constituent atoms are held together:

A

CAS number identifier assigned by the Chemical Abstracts Service. Globally, more than 350,000 chemical compounds (including mixtures of chemicals) have been registered for production and use.[1]

A compound can be converted to a different chemical substance by interaction with a second substance via a chemical reaction. In this process, bonds between atoms may be broken in either or both of the interacting substances, and new bonds formed.

Definitions

Any substance consisting of two or more different types of

subscripts to indicate the number of atoms involved. For example, water is composed of two hydrogen atoms bonded to one oxygen atom: the chemical formula is H2O. In the case of non-stoichiometric compounds, the proportions may be reproducible with regard to their preparation, and give fixed proportions of their component elements, but proportions that are not integral [e.g., for palladium hydride, PdHx (0.02 < x < 0.58)].[7]

Chemical compounds have a unique and defined

CAS number
.

There is varying and sometimes inconsistent nomenclature differentiating substances, which include truly non-stoichiometric examples, from chemical compounds, which require the fixed ratios. Many solid chemical substances—for example many silicate minerals—are chemical substances, but do not have simple formulae reflecting chemically bonding of elements to one another in fixed ratios; even so, these crystalline substances are often called "non-stoichiometric compounds". It may be argued that they are related to, rather than being chemical compounds, insofar as the variability in their compositions is often due to either the presence of foreign elements trapped within the crystal structure of an otherwise known true chemical compound, or due to perturbations in structure relative to the known compound that arise because of an excess of deficit of the constituent elements at places in its structure; such non-stoichiometric substances form most of the crust and mantle of the Earth. Other compounds regarded as chemically identical may have varying amounts of heavy or light isotopes of the constituent elements, which changes the ratio of elements by mass slightly.

Types

Molecules

Main article: molecule

A molecule is an

water
(two hydrogen atoms and one oxygen atom; H2O).

Ionic compounds

Main article:
Ionic compound

An ionic compound is a chemical compound composed of

simple ions such as the sodium (Na+) and chloride (Cl−) in sodium chloride, or polyatomic species such as the ammonium (NH+
4) and carbonate (CO2−
3) ions in ammonium carbonate. Individual ions within an ionic compound usually have multiple nearest neighbours, so are not considered to be part of molecules, but instead part of a continuous three-dimensional network, usually in a crystalline structure
.

Ionic compounds containing basic ions hydroxide (OH−) or oxide (O2−) are classified as bases. Ionic compounds without these ions are also known as salts and can be formed by acid–base reactions. Ionic compounds can also be produced from their constituent ions by evaporation of their solvent, precipitation, freezing, a solid-state reaction, or the electron transfer reaction of reactive metals with reactive non-metals, such as halogen gases.

Ionic compounds typically have high

dissolved they become highly conductive
, because the ions are mobilized.

Intermetallic compounds

Main article:
Intermetallic compound

An intermetallic compound is a type of metallic alloy that forms an ordered solid-state compound between two or more metallic elements. Intermetallics are generally hard and brittle, with good high-temperature mechanical properties.[14][15][16] They can be classified as stoichiometric or nonstoichiometic intermetallic compounds.[14]

Complexes

Main article: Coordination complex

A coordination complex consists of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents.[17][18][19] Many metal-containing compounds, especially those of transition metals, are coordination complexes.[20] A coordination complex whose centre is a metal atom is called a metal complex of d block element.

Bonding and forces

Compounds are held together through a variety of different types of bonding and forces. The differences in the types of bonds in compounds differ based on the types of elements present in the compound.

electrons in two adjacent atoms are positioned so that they create a temporary dipole. Additionally, London dispersion forces are responsible for condensing non polar substances to liquids, and to further freeze to a solid state dependent on how low the temperature of the environment is.[21]

A

periodic table of elements, yet it is observed between some metals and nonmetals. This is due to the mechanism of this type of bond. Elements that fall close to each other on the periodic table tend to have similar electronegativities, which means they have a similar affinity for electrons. Since neither element has a stronger affinity to donate or gain electrons, it causes the elements to share electrons so both elements have a more stable octet
.

anion. As outlined, ionic bonds occur between an electron donor, usually a metal, and an electron acceptor, which tends to be a nonmetal.[22]

electrostatic connection with another electronegative atom through interacting dipoles or charges.[23][24][25][26]

Reactions

Main article: Chemical reaction

A compound can be converted to a different chemical composition by interaction with a second chemical compound via a chemical reaction. In this process, bonds between atoms are broken in both of the interacting compounds, and then bonds are reformed so that new associations are made between atoms. Schematically, this reaction could be described as AB + CD → AD + CB, where A, B, C, and D are each unique atoms; and AB, AD, CD, and CB are each unique compounds.

The Hill System

The Hill System or also known as the Hill Notation is a form of writing chemical formulas idea by Edwin A. Hill. It is used to set the order of the Carbon atom as first and Hydrogen atom as the second of a chemical formula. Ex. C12H22O11 If the following chemicals are not present, the chemical formula should be written in alphabetic order. Ex. AgCNO[27]

See also

References

  1. PMID 31968937
    .
  2. ISBN 978-0-03-072373-5
  3. ISBN 9781442559462, archived
    from the original on 2021-05-31, retrieved 2020-12-08
  4. ISBN 978-0-13-140283-6, archived
    from the original on 2009-03-22
  5. ISBN 978-0-13-251210-7
  6. ^ "Chemical compound". ScienceDaily. Archived from the original on 2017-09-13. Retrieved 2017-09-13.
  7. S2CID 95343702. Phase diagram for Palladium-Hydrogen System
  8. ^
    ISBN 978-0-7167-5701-6
    .
  9. doi:10.1351/goldbook.M04002
  10. ISBN 978-0-395-43302-7
    .
  11. ISBN 978-0-13-066997-1
    .
  12. ISBN 978-0-07-115221-1
    .
  13. ISBN 978-0-669-41794-4
    .
  14. ^
    OCLC 903959750. Archived from the original on 2021-05-31. Retrieved 2020-11-10.{{cite book}}: CS1 maint: location missing publisher (link
    )
  15. OCLC 906692179. Archived
    from the original on 2021-05-31. Retrieved 2020-11-10.
  16. OCLC 300921090. Archived
    from the original on 2021-05-31. Retrieved 2020-11-10.
  17. ISBN 9780470687123
    .
  18. doi:10.1351/goldbook.C01203
  19. doi:10.1351/goldbook.C01330
  20. ISBN 978-0-08-037941-8
    .
  21. ^ "London Dispersion Forces". www.chem.purdue.edu. Archived from the original on 2017-01-13. Retrieved 2017-09-13.
  22. ^ "Ionic and Covalent Bonds". Chemistry LibreTexts. 2013-10-02. Archived from the original on 2017-09-13. Retrieved 2017-09-13.
  23. doi:10.1351/goldbook.H02899
  24. ^ "Hydrogen Bonds". chemistry.elmhurst.edu. Archived from the original on 2016-11-19. Retrieved 2017-10-28.
  25. ^ "Hydrogen Bonding". www.chem.purdue.edu. Archived from the original on 2011-08-08. Retrieved 2017-10-28.
  26. ^ "intermolecular bonding – hydrogen bonds". www.chemguide.co.uk. Archived from the original on 2016-12-19. Retrieved 2017-10-28.
  27. ISSN 0002-7863. {{cite journal}}: Check date values in: |date= (help
    )

Further reading

Look up chemical compound in Wiktionary, the free dictionary.
Wikimedia Commons has media related to Chemical compounds.
  • Robert Siegfried (2002), From elements to atoms: a history of chemical composition, American Philosophical Society,
    ISBN 978-0-87169-924-4
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