Question

The VSEPR Model is used for predicting the ______________ of the molecules.
1. Geometrical shapes
2. Bond length
3. Bond order
4. Number of resonating structure

Answer 1

Correct Answer - Option 1 : Geometrical shapes

The correct answer is Geometrical shapes.

• The VSEPR model used for predicting the geometrical shapes of molecules is based on the assumption that electron pairs repel each other and, therefore, tend to remain as apart as possible.
• According to this model, molecular geometry is determined by repulsions between lone pairs and lone pairs, lone pairs and bond pairs and bond pairs and bond pairs. 
• The order of these repulsions being: lone pairs - lone pairs > lone pairs - bond pairs > bond pairs - bond pairs.
• Sidgwick and Powell in the year 1940, proposed a simple theory based on the repulsive interactions of the electron pairs in the valence shell of the atoms.
• The VSEPR theory can predict the geometry of a large number of molecules, especially the compounds of p-block elements accurately.
• It is also quite successful in determining the geometry quite-accurately even when the energy difference between possible structures is very small.

• Bond length is defined as the equilibrium distance between the nuclei of two bonded atoms in a molecule.
• Bond lengths are measured by spectroscopic, X-ray diffraction, and electron diffraction techniques.
• Bond order is the number of bonds between the two atoms in a molecule.
  • In the Lewis description of the covalent bond, the bond Order is given by the number of bonds between the two atoms in a molecule.
  • With an increase in bond order, bond enthalpy increases and bond length decreases.
• The concept of resonance says that whenever a single Lewis structure cannot describe a molecule accurately, a number of structures with similar energy, positions of nuclei, bonding, and non-bonding pairs of electrons are taken as the canonical structures of the hybrid which describes the molecule accurately.