Question

a) First describe a small molecule, of no more than six atoms, where a Lewis Structure approach is inadequate to describe its bonding or observed properties.

b) Second, introduce the key ideas of bonding as interpreted by molecular orbital theory.

c) Third, choose examples from the course where the molecular orbital approach provides good explanation of structure, bonding and physical or chemical properties.

Answer 1

a) HCl is a small molecule having only Two Atoms which is Bonded by a Covalent Bond formed by the Sharing of a Single Electron with the Chlorine Atom.

Lewis Approches does not explains the Structure as well as Strength of this Acid as is it not having Co-ordinate Bonds in them.

b) Bonding by Molecular Orbital Theory states that the Atoms combines together to Form Molecular Orbitals ,either Bonding or Antibonding Molecular Orbitals by the Combination of the Atomic Orbitals in the Molecules and it can be used to determine the Electronic Structure of a Molecule by using Quantum Mechanics and also their Physical and Chemical Properties.

c) A Molecule whose Structure can be determined by MO Theory is Oxygen :

Oxygen has Electrons and they are Arranged in the various Molecular Orbitals as:

1s2, 2s2,2px2, 2py1 and 2 pz1

Here, 1s,2s and 2px are the Bonding Molecular Orbitals where Electrons are Paired and 2py and 2pz are the Antibonding MO where Electron is Unpaired.

This can Conclude that Oxygen is Paramagnetic in Nature.