Dragos Rule - Practice Questions & MCQ

Bond Angle

Bond angle is the angle between two bonds that formed between two atoms. The figure given below illustrates the concept.

Drago’s Rule

Drago’s rule is an empirical rule that is used to explain the bond angles of hydrides of group 14, 15 and 16 and 2nd member of each of these three groups.

According to Drago’s rule when the various conditions are satisfied as mentioned below, then the energy difference will be very high between the participating atomic orbitals and hence no mixing of orbitals or hybridization takes place.

• At least one lone pair must be present on the central atom.

• The central atom must be of or below 3rd period.

• The electronegativity of the surrounding atoms must be less than or equal to 2.1.

• For these hydrides, hybridization does not take place and thus bonding takes place only through pure atomic p orbitals like in PH₃ and hence the bond angle will be approximately 90⁰.

For example, the bond angle for H₂O is 104.50 but for S₂H, Se₂H and Te₂H, the bond angles are approximately 90⁰.