What is the hybridisation of Br in BrF5 and BrF3 respectively? 

CONCEPT:

Hybridization

• Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals suitable for the pairing of electrons to form chemical bonds in valence bond theory.
• The type of hybridization can be determined by the steric number, which is the sum of the number of atoms bonded to the central atom and the number of lone pairs on the central atom.

EXPLANATION:

• For BrF₅:
  • The central atom, Br, is bonded to 5 F atoms and has 1 lone pair of electrons.
  • The steric number = 5 (bonded atoms) + 1 (lone pair) = 6.
  • Hybridization with a steric number of 6 is sp³d².
    
• For BrF₃:
  • The central atom, Br, is bonded to 3 F atoms and has 2 lone pairs of electrons.
  • The steric number = 3 (bonded atoms) + 2 (lone pairs) = 5.
  • Hybridization with a steric number of 5 is sp³d.
    

Therefore, the hybridization of Br in BrF₅ and BrF₃ is sp³d² and sp³d respectively.