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More on Ionic Compounds and Ionic Bonds
I. Ionic compounds are held together as ions in a crystal or
“lattice” structure by ionic bonds.
A. Lattice = “regular arrangement” in repeating patterns.
B. Ions are charged atoms. Examples: Na+ ; ClC. In ionic bonds, ions are held together by
electrostatic force between oppositely charged
atoms.
1. “Opposite charges attract each other” =
electrostatic force.
D. Ionic compounds have the following traits:
1. They have a high melting point.
2. They have a high boiling point.
3. They are hard and very brittle.
4. They conduct electricity well when dissolved
in water.
5. They don’t conduct heat well.
E. In ionic compounds, the positively charged
atom is called a cation (“positive cat”)
F. The negatively charged atoms is called an
anion (“negative Ann”)
II. In the crystal structure of sodium chloride (NaCl):
A. The sodium atom is a cation (Na+)
B. The chlorine atom is an anion (Cl-)
III. Most importantly, the chemical formula only
tells you the repeating “units” that connect
in a certain lattice (crystal) structure to make
the compound.
A. For NaCl, it’s:
Na+
Cl-
NaCl (this is the repeating
unit for the crystal)
Ionic compound
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 an
anion 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 are hard and very brittle.
The crystal structure of sodium chloride, NaCl, a typical ionic compound. The purple spheres are sodium cations, Na+, and the
green spheres are chloride anions, Cl−.
Ions can be single atoms, as the sodium and chloride in common table salt sodium chloride, or more complex groups
such as the carbonate in 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 do not occur. (For an easily visible analogy, experiment with a pair of bar magnets.)
Chemical compounds are never strictly ionic. Even the most electronegative/electropositive pairs such as caesium
fluoride exhibit a degree of covalency. Similarly, covalent compounds often exhibit charge separations. See also
HSAB theory.
Contents:
1. Physical properties
2. Characteristics
3. Solubility
4. Electricity conductivity
5. Name
6. See also
7. References
1. Physical properties
Physical Properties Ionic Compounds States(at room temperature) Solid Electrical conductivity Solid: No Liquid: Yes
Aqueous: Yes (if soluble) Boiling point and Melting Point High Solubility in water Often high Thermal conductivity
Low
2. Characteristics
Ionic compounds have strong electrostatic bonds between particles. As a result, they generally have very 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 usually form crystals, organic ionic liquids are of increasing
interest.
The ions produced by electron transfer attract each other by electrostatic attraction and this creates an ionic bond.
3. Solubility
Following the aphorism, "like dissolves like", ionic compounds dissolve in polar solvents, especially those that 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.
When the oppositely charged ions in the solid ionic lattice are surrounded by the opposite pole of a polar molecule,
the solid ions are pulled out of the lattice and into the liquid. When this force is more than the electrostatic attraction
of the lattice, the ions become dissolved in the liquid.
4. Electricity conductivity
Solid ionic compounds cannot conduct electricity because there are no mobile ions or electrons present in the lattice.
When the ionic compounds are dissolved in a liquid or molten, they can conduct electricity with the mobile ions.
5. Name
According to the IUPAC, an ionic compound's common name is written using two words. The name of the cation
comes first (when using stock nomenclature with the oxidation number written in parentheses, followed by the name
of the anion. [1] For example, Fe2(SO4)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)).