NATURE OF BONDING AND PROPERTIES:
Properties of the compounds depend upon the nature of bonding present in them. The compounds having very strong bonding are mostly solid, and those having very weak bonding are gases.
Ionic compounds: The compounds which are formed due to ionic bonding are called ionic compounds.
Explanation: Ionic compounds are made up of positively and negatively charged ions. Thus they consist of ions and not the molecules. These positively and negatively charged ions are held together in a solid or crystal form with strong electrostatic attractive forces.
Properties of ionic compounds: The ionic compounds have following properties:
- Ionic compounds are mostly crystalline solids.
- Ionic compounds in solid state have negligible electrical conductance but they are good conductors in solution and in the molten form. It is due to presence of free ions in them.
- Ionic compounds have high melting and boiling points. For example, sodium chloride has melting point 800 °C and a boiling point
1413 °C. As ionic compounds are made up of positive and negative ions, there exist strong electrostatic forces of attraction between oppositely charged ions. So, a great amount of energy is required to break these forces.
- They dissolve easily in polar solvents like water. Water has high dielectric constant that weakens the attraction between ions.
Covalent compounds: The compounds that are formed due to covalent bonding (sharing of electrons) are called Covalent compounds.
Explanation: These compounds are formed by mutual sharing of electrons and are molecular in nature. Covalent compounds are made up of two or more non metals. Examples: H2, CH4, CO2 , H2SO4 , C6 H12 O6 .
General properties of covalent compound: General properties shown by covalent compound are as follows:
- They have usually low melting and boiling points.
- They are usually bad conductors of electricity. The compounds having polar character in their bonding are conductor of electricity
when they dissolve in polar solvents.
- They are usually insoluble in water but are soluble in non-aqueous solvents like benzene, ether, alcohol and acetone.
- Large molecules with three dimensional bonding form covalent crystals which are very stable and hard. They have very high melting and boiling points.
Properties of polar and non polar compounds: Compounds that contain polar covalent bond are called polar compounds and that contain non polar covalent bond are called non polar compounds.
Explanation; Polarity in a Chemical bond is due to difference in electronegativities of the bonding atoms. On the Pauling Scale, fluorine has been given an electronegativity value of 4.0. The values for other elements are calculated relative to it. The covalent compounds having more electronegativity difference are much polar and vice versa.
|Polar covalent compounds||Non polar covalent compounds|
|Polar covalent compounds dissolves in water.||Non polar covalent compounds donot dissolve in water.|
|They conduct electricity in water due to formation of ions.||They donot conduct electricity.|
Coordinate Covalent Compounds: The compounds containing coordinate covalent bond are called coordinate covalent compounds.
Properties: Their properties are mostly similar to those of covalent compounds. As the nuclei in these compounds are held by shared pair of electrons, therefore, they do not form ions in water. Due to their covalent nature they form solutions in organic solvents and are very less soluble in water. Usually they are rigid compounds with a dipole.
Metals: Metals have common property of conducting heat and electricity. It gives them prime role in many industries. Major properties
shown by the metals are as follows:
- They show metallic lustre.
- They are usually malleable and ductile. Malleability is the property by virtue of which a metal can be rolled into sheets, while
ductility is the property by virtue of which a metal can be drawn into wires.
- They have usually high melting and boiling points.
- Being greater in size they have low ionization energies and form cations (M+) very easily.
- They are good conductors of heat and electricity in solid and liquid state due to mobile electrons.