What is meant by hybridization of atomic orbitals? Describe the shapes of sp, sp², sp³ hybrid orbitals.

Distinguish between a sigma (σ) bond and a pi  bond.

263.

Use molecular orbital theory to explain why the Be₂ molecule does not exist. 

Descibe the hybridisation in case of PCl₅. Why are the axial bonds longer as compared to equatorial bonds?

Define hydrogen bond. Is it weaker or stronger than the van der Waals forces?

What is meant by the term bond order? Calculate the bond order of: 

The species in which the N atom is in a state of sp hybridization is:

• NO₂^-

• NO₃^-

• NO₂
  

• NO₂
  

The ionic radii (in Å) of N^3–, O^2– and F^– are respectively:

• 1.36, 1.40 and 1.71

• 1.36, 1.71 and 1.40

• 1.71, 1.40 and 1.36

• 1.71, 1.40 and 1.36

In which of the following pairs of molecules/ions, both the species are not likely exist?

Which of the following exists as covalent crystals in the solid state?

• Iodine

• Silicon

• Sulphur

• Sulphur