CBSE Class 10 Answered
A covalent bond is a form of chemical bonding that is characterized by the sharing of pairs of electrons between atoms, or between atoms and other covalent bonds. In short, attraction-to-repulsion stability that forms between atoms when they share electrons is known as covalent bonding.
Covalent bonds are formed as a result of the sharing of one or more pairs of bonding electrons. Each atom donates half of the electrons to be shared. This sharing of electrons is as a result of the electronegativity(electron attracting ability) of the two bonded atoms are either equal or the difference is no greater than 1.7. If the electronegativity difference is greater than 1.7 then the higher electronegative atom has an electron attracting ability large enough to force the transfer of electrons from the less electronegative atom. This would be an ionic bond. As long as the electronegativity difference is no greater than 1.7 the atoms can only share the bonding electrons.
The covalent bonds within these molecules are at least as strong as an ionic bond, but we don't have to break these covalent bonds to separate one Cl2 molecule from another. As a result, it is much easier to melt Cl2 to form a liquid or boil it to form a gas, and Cl2 is a gas at room temperature.
The difference between ionic and covalent bonds also explains why aqueous solutions of ionic compounds conduct electricity, while aqueous solutions of covalent compounds do not. When a salt dissolves in water, the ions are released into solution
Ionic and covalent bonds differ in the extent to which a pair of electrons is shared by the atoms that form the bond. When one of the atoms is much better at drawing electrons toward itself than the other, the bond is ionic. When the atoms are approximately equal in their ability to draw electrons toward themselves, the atoms share the pair of electrons more or less equally, and the bond is covalent. As a rule of thumb, metals often react with nonmetals to form ionic compounds or salts, and nonmetals combine with other nonmetals to form covalent compounds. This rule of thumb is useful, but it is also naive, for two reasons.
- The only way to tell whether a compound is ionic or covalent is to measure the relative ability of the atoms to draw electrons in a bond toward themselves.
- Any attempt to divide compounds into just two classes (ionic and covalent) is doomed to failure because the bonding in many compounds falls between these two extremes.
The first limitation is the basis of the concept of electronegativity. The second serves as the basis for the concept of polarity.
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