Covalent compounds are rubbery in nature and have low hardness Metals are

Covalent compounds are rubbery in nature and have low

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Covalent compounds are rubbery in nature and have low hardness. Metals are crystalline in nature but are soft and have high ductility. 2 Ionic crystals are built up of oppositely charged ions. Giant molecules are formed as each ion tends to attract maximum of opposite nature around itself due to electrostatic forces working in all directions. Covalent crystals are built up of molecules instead of ions. They are formed by sharing of electron pairs between atoms of the same or different elements. They are formed when electrons delocalize themselves from particular atoms and form an electron cloud. 3 They have high melting and boiling point as the strong electro-static forces are working in all directions. They have low melting and boiling point as they are held together by weak intermolecular forces. They have a slightly lower melting and boiling point than ionic compounds. 4 Ionic compounds have poor electrical conductivity. Covalent compounds are non- conductors. Metals have high electrical conductivity. 5 Ionic compounds are closed packed type structures. Covalent compounds have open structures. Metals have open structures. 6 Ionic compounds are soluble in water and polar solvents like ammonia but insoluble in organic solvents. Covalent compounds are insoluble in water but soluble non-polar solvents such as benzene, alcohol, chloroform. Metals are neither soluble in water nor in benzene. 7 Ionic compounds exist in the solid form only. Covalent compounds exist in solid, liquid and gaseous form. Metals exist in solid form (except mercury).
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~ Page 46 of 79 ~ EXERCISE 1. Briefly explain the difference between an atom and an ion. 2. Briefly explain what is meant by the term isotope. 3. State the name given to non-crystalline solids. 4. How do atoms achieve stable configuration? 5. State the charge and name each of the following: (a) atoms which lose electrons; (b) atoms which gain electrons. 6. Name the kind of bond formed in the following situations: (a) electrostatic attraction between oppositely charged ions; (b) sharing of electrons between atoms of the elements being bonded; (c) electrostatic attraction between ions and delocalised electrons. 7. Compare and contrast metallic, covalent and ionic bonds. 8. Briefly explain how metallic bonding differs from ionic bonding. 9. Briefly explain the electron cloud and its role in the metallic bond.
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~ Page 47 of 79 ~ LATTICE STRUCTURES The molecules of a liquid or gas though in close contact are not bound in fixed positions but are free to move about. But as the temperature of a liquid is lowered, the thermal motion of the molecules decreases and at the cooling point, the motion is slow enough that the attractive forces between the molecules are able to lock the molecules into fixed positions.
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