Periodic Properties

Step 1: Understanding the Concept:
Polarity in these isoelectronic cyclic molecules depends on the electronegativity difference ( ) between the alternating atoms in the ring.
Step 2: Detailed Explanation:
1. Benzene ( ): It is a non-polar hydrocarbon. The and bonds have negligible , and its high symmetry ( ) ensures a net dipole moment of zero.
2. Borazine ( ): Known as "inorganic benzene". The bond is polar because and , giving . While the symmetric ring has , it has significant "local" bond polarity.
3. Boroxine ( ): Contains alternating B and O atoms. Since Oxygen is more electronegative ( ) than Nitrogen ( ), the bond ( ) is much more polar than the bond.
Higher leads to higher ionic character and higher polarity in the molecule's chemical behavior.
Step 3: Final Answer:
The polarity order is Boroxine > Borazine > Benzene.