Question

What is dragos rule . Explain with an example in detail

Answer 1

Drago’s rule is an empirical rule and is used to explain the bond angles of hydrides of group 15 and 16 of or below 3rd period. So essentially it is only applicable for PH3, AsH3,SbH3 and H2S, H2Se, H2Te.

According to drago,s rule when the following conditions are satisfied, then the energy difference between the participating atomic orbitals will be very high and thus no mixing of orbitals or hybridization takes place.

1. Atleast one lone pair must be present on the central atom.
2. The central atom must be of or below 3rd period.
3. The electronegativity of the surrounding atom must be less than equal to 2.1.
4. No hybridisation means bonding will take place through pure atomic p orbitals in PH3 and thus bond angle will be approximately 90.

Eg :- PH3 which has a bond angle of 90 degree (pure p orbitals, no hybridisation)