Melting Point
Ionic
compounding are typically solid and usually have high melting and boiling
points. In contrast covalent compound are typically gases, liquids or low
melting solids. These differences occur because of differences in bonding and structure.
Ionic compounds are made up of positive and negative ions arranged in a regular
way in a lattice. The attraction between ions is electrostatic and is
non-directional, extending equally in all direction. Melting of the compound involves
breaking of the lattice. This requires considerable energy and hence melting
and boiling points are usually high and the compounds are very hard. Compounds
with covalent bonds are usually made up of discrete molecule. The bonds are
directional and strong covalent bonding forces hold the atom together to make a
molecule. In the solid molecules are held together by weak Vander Waals forces. To melt or boil the compound we simply have to
supply amount of energy to break Vander Waal forces. Hence compounds are often
gases, liquid or soft solids with low melting points.
§ Melting- Change from
solid to liquid
§ Melting Point- Specefic
tempreture whem melting occurs
§ Each pure substance has
a specific melting point.
Example;
Melting point for water-0oC (32oF)
Melting point for Nitrogen- (-209.9oc)
Melting point for Silver- 961.93
oC
Melting
point for Corban- 3500.0oC
Conductivity
Ionic
compounds conduct electricity when the compound is melted or in aqueous
solution. Conduction is achieved by the ions migrating towards the electrodes
under the influence of electric potentials. Covalent compounds contain neither
ions nor mobile electrons so they are unable to conduct electricity in either
solid or gaseous state.
Solubility
Ionic
compounds are usually soluble in polar solvents. There are solvents if high
dielectric constant such as water or mineral acids. Covalent compounds are not normally
soluble in polar solvents but they are soluble in non-polar solvents of low dielectric
constant such as benzene or CCl4.
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