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Chemical Bonding and Molecular Structure

Long Answer Type

251.

Why does ice float over water?

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252.

Give reasons for the following:
(i) Density of water is maximum at 277K (4°C).
(ii) Why glycerol (glycerine) is more viscous than ethyl alcohol?

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Short Answer Type

253.

Explain the formation of a chemical bond.

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Long Answer Type

254.

Write Lewis symbols for the following atoms and ions:
S and S^2–; Al and Al³⁺; H and H^–.

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Short Answer Type

255.

Define octet rule. Write its significance and limitations.

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256.

Write three favourable factors for formation of ionic bond.

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257.
Define bond length.

Bond length: Bond length is defined as the equilibrium internuclear separation distance of the bonded atoms in a molecule. Each atom of the bonded pair contributes to the bond length.

In the case of a covalent bond, the contribution from each atom is called covalent radius of that atom.
The bond length in a covalent molecule AB
R = r _A + r _B
where R is the bond length; r_Aand r_B are the covalent radii of atoms A and B respectively.

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