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Chemical Bonding and Molecular Structure — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryChemical Bonding and Molecular Structure5 Marks
Question
Give reasons for the following:
  1. Covalent bonds are directional bonds while ionic bonds are non- directional.
  2. Water molecule has bent structure whereas carbon dioxide molecule is linear.
  3. Ethyne molecule is linear.
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Answer

  1. Since the covalent bond depends on the overlapping of orbitals between different orbitals, the geometry of the molecule is different. The orientation of overlap is different. The orientation of overlap is the factor responsible for their directional nature.
  2. Due to presence of two lone pairs of electrons on oxygen atom in HiO the repulsion between is more. $\mathrm{CO}_2$ undergoes sp hybridization resulting in linear shape $(\mathrm{O}=\mathrm{C}=\mathrm{O})$ while $\mathrm{H}_2 \mathrm{O}$ undergoes $\mathrm{sp}^3$ hybridisation resulting in distorted tetrahedral or bent structure.
  1. In ethyne molecule carbon undergoes sp hybridization with two unhybridised orbitals. One sp hybrid orbital of one carbon atom overlaps axially with sp hybrid orbital of the other carbon atom to form C – C sigma bond while the other hybridized orbital of each carbon atom overlaps axially with S orbitals of hydrogen atoms forming. Unhybridised orbitals form n-bonds.
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