Question 7 of 34intermediate🔍 AnalyzeShort Answer2 marks

Explain [Co(NH3)6]3+ is an inner orbital complex whereas [Ni(NH3)6]2+ is an outer orbital complex.

Correct Answer

In [Co(NH3)6]3+, cobalt is in +3 oxidation state with electronic configuration 3d6. In the presence of NH3, the 3d electrons pair up leaving two d orbitals empty. This allows for d2sp3 hybridisation using inner d orbitals (3d), making it an inner orbital complex. The complex is diamagnetic due to absence of unpaired electrons.

In [Ni(NH3)6]2+, nickel is in +2 oxidation state with d8 configuration. Due to the presence of 8 electrons in d orbitals, pairing cannot create two empty d orbitals for d2sp3 hybridisation. Therefore, sp3d2 hybridisation occurs using outer d orbitals (4d), making it an outer orbital complex.

Exercise: Intext Questions | Q: 5.8 | (Page Page 18)
For More Understanding

Explanation

The context clearly explains that in [Co(NH3)6]3+, the 3d electrons pair up leaving two d orbitals empty for d2sp3 hybridisation, using inner d orbitals. For [Ni(NH3)6]2+, Ni has d8 configuration and cannot achieve d2sp3 hybridisation, so it uses sp3d2 hybridisation with outer d orbitals. The key difference lies in the electronic configuration and whether inner d orbitals can be used for hybridisation.

Solution Steps

  1. Step 1: Identify oxidation state and electronic configuration of Co3+ (3d6) and Ni2+ (3d8)

  2. Step 2: For Co3+, electrons pair up leaving two empty 3d orbitals for d2sp3 hybridisation (inner orbital)

  3. Step 3: For Ni2+, d8 configuration cannot provide two empty inner d orbitals, so sp3d2 hybridisation uses outer 4d orbitals

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