Chemical species - Ion, Free Radical and Their Types - Home of Knowledge

Chemical species – Ion, Free Radical and Their Types

Chemical species: Atom or group of atoms which can take part in a chemical reaction or that is produced after a chemical reaction as a highly reactive substance is called chemical species.

Types of chemical species: Following are the main types of chemical species.

1) ions  2) Free Radicals.

1) Ion is an atom or group of atoms having a charge on it. The charge may be positive or negative. On the basis of charge assigned to an ion, there are two types of ions.

A) Cations B) Anions.

A) Cations :An atom or group of atoms having positive charge on it is called cation.  For example, Na+, K+are cations. The cations are of two types.

I)Atomic cation:An atom having positive charge on it is called atomic cation. Examples: Na+, Ca+, H+, etc.

II)Molecular cation(cationic molecular ion)Agroup of atoms or molecule having positive charge on it is called molecular cation. Examples: NH4+, H3O+, etc.

Formation of cations: cation are formed when atom(s) lose electrons from their outermost shells. The following equations show the formation of cations from atoms.

Atom ===> Positive charged species + electron or electrons

Na ===> Na+ + 1e

B) Anion: An atom or a group of atoms that has a negative charge on it, is called anion.

Types of anions: anions are of two types.

I) Atomic anion:An atom that has a negative charge on it, is called atomic anion. EXAMPLES: O-2, Cl, F, etc.

II)Molecular anion (anionic molecular ion): A group of atoms that has a negative charge on it, is called anion.

Examples: SO4-2, H2PO4, etc.

Formation: Anion is formed by the gain or addition of electrons to an atom. For example, Cl and O2-. Following examples show the formation of an anion by addition of electrons to an atom.

Cl + 1e ====> Cl

  • Molecular ion:Group of atoms or molecule having a charge on it is called molecular ion. Molecular ions are of two types.

 

I)Molecular cation(cationic molecular ion) :Agroup of atoms or molecule having positive charge on it is called molecular cation. Examples: NH4+, H3O+

 

II)Molecular anion(anionic molecular ion) Agroup of atoms or molecule having negative charge on it is called molecular anion. Examples: SO4-2, H2PO4-, etc.

Free Radicals:

Free radicals are atoms or group of atoms possessing odd number of (unpaired) electrons. It is represented by putting a dot over the symbol of an element e.g. H., CI., H3C.. Free radicals are generated by the homolytic (equal) breakage of the bond between 3 two atoms when they absorb heat or light energy. A free radical is extremely reactive species as it has the tendency to complete its octet.

 

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