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Chapter No.4 - Chemical Bonding
Questions And Answers
Q. : Write down differences between:
Polar and Non Polar Bonds
Polar and Non Polar Compounds
Ans: Difference Between Polar and Non Polar Bonds
| S.NO. | Polar Bonds | Non Polar Bonds |
|---|---|---|
| 1. | Polar bond is formed between two unlike (dissimilar) atoms with different electronegativities. | Non polar bond is formed between two identical (similar) atoms with same electronegativities. |
| 2. | In a polar bond the electrons are not shared equally by the bonded atoms. | In a non polar bond the electrons are equally shared by the bonded atoms. |
| 3. | A polar bonds has partially positive and negative poles (ends) e.g.: Hઠ+ - Clઠ- | A non polar bonds is electrically neutral having no partially positive (+ve) and negative (-ve) poles (ends) |
| 4. | A polar bond is short and strong | A non polar bond is longer and less than a polar bond. |
| 4. | Few examples of polar covalent bonds are NH3, H2O, HCl. etc. | Few examples of non-polar covalent compounds are H2 (H-H), O2 (O=O), N2 (N=N) |
Difference Between Polar and Non Polar Compounds
| S.NO. | Polar Compounds | Non Polar Compounds |
|---|---|---|
| 1. | Polar covalent compounds are soluble in water. | Non polar covalent compounds are generally insoluble in water. |
| 2. | Polar covalent compounds usually conduct electricity due to the formation of ions with water. | Non-polar covalent compounds do not conduct electricity in the solid, molten or aqueous solution. |
| 3. | Polar covalent compounds insoluble in non-polar solvent. | Non-polar covalent compounds are soluble in non-polar solvent like petrol, benzene etc. |
| 4. | Few examples of polar covalent compounds are H2SO4, H2O, HCl, HF, HBr, HI | Few examples of non-polar covalent compounds are CO2, CH4, C2H6. |
Q. : What is co-ordinate covalent bond? Explain it with examples?
Ans: Coordinate Covalent Bond or Dative Covalent Bond:
Co-ordinate covalent bond is a special type of covalent bond. Each atom contributes one electron to form a covalent bond. However, covalent bond can be formed between two atoms even when only one of the atoms contributes both electrons constituting the covalent bond. As a result the bond has a partial (partly) ionic characters. Such a bond is called as a coordinate covalent bond or dative bond.
Definition:
Thus, we can define a coordinate covalent bond as:
"The type of bond in which bond pair of electrons is contributed by one atom only, is called coordinate covalent or dative covalent bond."
Concept of donor and acceptor:
The atom that donates the electron pair is called the donor and the other atom which accepts the electron pair is called acceptor. A coordinate covalent bond is represented by an arrow (⟶) pointing towards the atom which accepts the electron pair. The pair of unshared valance electrons possessed by the donor is called a lone pair.
Nature Of Coordinate Covalent Bond or Dative Covalent Bond:
Once a bond is formed, there is no difference between the dative covalent and ordinary covalent bonds in reality. The only difference between the two is a mode of formation. Due to their covalent nature of bond formation, the properties of these compounds are similar to those of covalent compounds.
Examples:
A few examples of formation of a coordinate covalent bond are given as under:
1. Ammonium Chloride:
The reaction between ammonia and hydrogen chloride involves the formation of a dative bond between N atom in NH3 containing lone pairs and H+ ion from HCl. When ammonia reacts with hydrogen ions (H+) in an aqueous solution of an acid, the hydrogen ion is attracted to the lone pair and a coordinate covalent bond is formed.
2. Hydronium Ion:
When hydrogen chloride dissolves in water, hydrogen ion is attracted to the lone pair of electrons which is available on oxygen and hydronium ion is formed as shown below:
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