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Chemical Bonding and Molecular Structure

Long Answer Type

151.
Discuss the orbital shapes of the following covalent molecules:
(i) HF (ii) H₂O (iii) NH₃.

(i) Hydrogen fluoride molecule (HF): The electronic configuration of hydrogen is 1s¹. Electronic configuration of Fluorine is 1s² 2s² 2p⁵. Therefore half-filled orbital of hydrogen atom overlaps with the half filled 2p-orbital of fluorine atom to form H – F molecule.

(ii) A water molecule (H₂O): The electronic configuration of hydrogen is 1s¹. Electronic configuration of oxygen 1s² 2s² 2p⁴. Therefore half-filled orbital of each hydrogen atom overlaps with each of the half-filled 2p–orbitals having electrons in opposite spins of oxygen atom to form H₂O molecule.

(iii) Ammonia molecule (NH₃): The electronic configuration of hydrogen is 1s¹. Electronic configuration of nitrogen is 1s² 2s² 2p³. Therefore the orbital of each hydrogen atom overlaps with each of the three nitrogen orbitals.

half-filled 2p orbitals of nitrogen having electrons in opposite spin to form NH₃molecule.

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Short Answer Type

152.

Why is a sigma bond stronger than pi bond ?

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153.

Why are lone pair-lone pair repulsion stronger than lone pair-bond pair.

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Long Answer Type

154.

Describe, in brief, the types of covalent bonds ?

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155.

Using the orbital overlap concept, explain the formation of:
(i) O₂ molecule (ii) N₂ molecule.

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156.

Distinguish between a sigma $open parentheses straight sigma close parentheses$ bond and a $pi space left parenthesis straight pi right parenthesis$ bond.