Everything about Ionic Compound totally explained
In
chemistry, an
ionic compound is a
chemical compound in which
ions are held together in a lattice structure by
ionic bonds. Usually, the positively charged portion consists of metal
cations and the negatively charged portion is a
halogen or polyatomic ion. Ions in ionic compounds are held together by the
electrostatic force between oppositely charged bodies. Ionic compounds have a high melting and boiling point, and they've a high hardness and are very brittle.
Ions can be single atoms
, as in common table salt
sodium chloride, or more complex groups such as
calcium carbonate. But to be considered an ion, they must carry a positive or negative charge. Thus, in an ionic bond, one 'bonder' must have a positive charge and the other a negative one. By sticking to each other, they resolve, or partially resolve, their separate charge imbalances. Positive to positive and negative to negative ionic bonds don't occur. (For an easily visible analogy, experiment with a pair of bar
magnets.)
Chemical compounds are rarely strictly ionic or strictly covalent. Except for the most
electronegative/
electropositive pairs such as
caesium fluoride, ionic compounds usually exhibit a degree of covalency. Similarly,
covalent compounds often exhibit charge separations. See also
HSAB theory.
Physical properties of ionic and molecular compounds:
|
Ionic compounds |
Molecular compounds |
| States (at RTP) |
Solid |
Can be solid, liquid or gas at room temperature |
| Electrical conductivity |
Solid: no
Molten: yes |
No |
| Boiling point |
High |
Low |
| Solubility in water |
Often high |
Variable; usually lower than ionic |
| Thermal conductivity |
Low |
Low |
Characteristics
Ionic compounds have strong
electrostatic bonds between particles. As a result, they generally have high melting and boiling points. They also have good electrical conductivity when molten or in aqueous solution. While ionic
inorganic compounds are solids at room temperature and will usually form crystals, organic
ionic liquids are of increasing interest.
Solubility
Following the aphorism, "like dissolves like", ionic compounds dissolve in
polar solvents, especially those which ionize, such as water and
ionic liquids. They are usually appreciably soluble in other polar solvents such as
alcohols,
acetone and
dimethyl sulfoxide as well. Ionic compounds tend not to dissolve in
nonpolar solvents such as
diethyl ether or
petrol (gasoline).
When an ionic compound is named, the cation is named first and then the anion. When an elemental anion is named, the suffix, -ide, is added to the name of the element. There are two common types of cations: Type I and Type II. Type I cations have only one charge and their name is simply listed when the compound is named. Type II cations have more than one charge and when the ionic compound is named, a Roman numeral is used to denote the charge of the cation.
In addition, there are common polyatomic anions which don't have suffixes in their name such as hypochlorite (ClO
–).
Nomenclature
According to the
IUPAC, an ionic compound's common name is written using two words. The name of the cation comes first (when using the
Stock system) with the
oxidation number written in parenthesis, followed by the name of the anion. For example, Fe
2(SO
4)
3 is named as iron(III) sulfate. If the Classical naming system is being used, some ionic compounds have special "old" names, such as ferric (iron(III)), ferrous (iron(II)), cupric (copper(II)), and cuprous (copper(I)).
Further Information
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