Chemical species are a specific form of

chemical substance A chemical substance is a unique form of matter with constant chemical composition and characteristic properties. Chemical substances may take the form of a single element or chemical compounds. If two or more chemical substances can be com ...

or chemically identical molecular entities that have the same molecular energy level at a specified timescale. These entities are classified through bonding types and relative abundance of

isotope Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their Atomic nucleus, nuclei) and position in the periodic table (and hence belong to the same chemica ...

s. Types of chemical species can be classified based on the type of

molecular entity In chemistry and physics, a molecular entity, or chemical entity, is "any constitutionally or isotopically distinct atom, molecule, ion, ion pair, radical, radical ion, complex, conformer, etc., identifiable as a separately distinguishable en ...

and can be either an atomic, molecular, ionic or radical species.

Classification

Generally, a chemical species is defined as a chemical identity that has the same set of molecular energy levels in a defined timescale (i.e. an experiment). These energy levels determine the way the chemical species will interact with others through properties such as bonding or isotopic compositions. The chemical species can be an atom, molecule, ion, or radical, with a specific chemical name and

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

. In

supramolecular chemistry Supramolecular chemistry refers to the branch of chemistry concerning Chemical species, chemical systems composed of a integer, discrete number of molecules. The strength of the forces responsible for spatial organization of the system range from w ...

, chemical species are structures created by forming or breaking bonds between molecules, such as

hydrogen bond In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, Covalent bond, covalently b ...

ing, dipole-dipole bonds, etc. These types of bonds can determine the physical property of chemical species in a liquid or solid state. The term is also applied to a set of chemically identical atomic or molecular structures in a solid compound. Table salt with salt shaker V1

Types of Chemical Species

Atomic species: Specific form of an element defined by the atom's isotope, electronic or oxidation state.

Argon Argon is a chemical element; it has symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as abu ...

is an

atom Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...

ic species of formula Ar. Molecular species: Groups of atoms that are held together by

chemical bond A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons a ...

s. An example is

ozone Ozone () (or trioxygen) is an Inorganic compound, inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , break ...

, which has the chemical formula . Ionic species: Atoms or molecules that have gained or lost

electron The electron (, or in nuclear reactions) is a subatomic particle with a negative one elementary charge, elementary electric charge. It is a fundamental particle that comprises the ordinary matter that makes up the universe, along with up qua ...

s, resulting in a net electrical charge that can be either positively (cation) or negatively charged (anion). * Species with an overall positive charge will be a cationic species. The

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

ion is an example of a cationic species and its formula is Na⁺. * Species with an overall negative charge will be an anionic species. Chloride is an anionic species, and its formula is Cl⁻. Radical species: Molecules or atoms with unpaired electrons. Triarylborane anion is a radical species and its formula is Ar3B⁻ Chemicals can be two different types of species. For example,

nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...

is a molecular and ionic species, with its formula being NO₃⁻. Note that DNA is not a species; the name is generically applied to many molecules of different formulas (each DNA molecule is unique).{{Cite journal , last=Caruthers , first=Marvin H. , date=January 2013 , title=The Chemical Synthesis of DNA/RNA: Our Gift to Science , journal=Journal of Biological Chemistry , volume=288 , issue=2 , pages=1420–1427 , doi=10.1074/jbc.x112.442855 , doi-access=free , issn=0021-9258 , pmc=3543024 , pmid=23223445

References

Chemical substances

Classification

Types of Chemical Species

See also

References