Chemistry For Class IX (New Book ) - Chapter No.4 - Chemical Bonding - Questions And Answers

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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: