Revision: Coordination Compounds Chemistry HSC Science (General) 12th Standard Board Exam Maharashtra State Board

Anomers are stereoisomers of sugars that differ only in the configuration of the hydroxyl group at the C₁ position. They are not mirror images of each other.

Postulates:

• A covalent bond forms when orbitals of two atoms, each containing one unpaired electron, overlap with each other.
• The overlapping of two atomic orbitals produces a localised molecular orbital called a bonding orbital, occupied by two electrons with opposite spins.
• Maximum electron density lies between the two nuclei (internuclear region).
• The greater the overlap, the stronger the bond and the greater the bond energy — but the shorter the bond length.
• Electrostatic attraction between the nuclei and the accumulated electron cloud between them provides the binding force of the covalent bond.

Types of Orbital Overlap

Axial (head-on) overlap → forms σ (sigma) bond:

• s-s overlap: Two half-filled s orbitals overlap along the internuclear axis
• s-p overlap: Half-filled s and half-filled p orbital overlap along internuclear axis
• p-p overlap (axial): Two half-filled p orbitals overlap along the internuclear axis

Lateral (side-on) overlap → forms π (pi) bond:

• p-p overlap (lateral): Two half-filled p orbitals overlap side-ways (perpendicular to internuclear axis)