For the coordination compound [Ni(en)₂]SO₄:

i. Provide the name of the coordination compound.

ii. Identify the oxidation number of Ni.

iii. Sketch its crystal field energy-level diagram.

iv. Classify the complex as either high-spin or low-spin.

v. Identify the number of unpaired electrons, if any.

Consider the following nickel(II) complexes NiCl₂(PEt₃)₂ and Ni(NO₃)₂(PEt₃)₂. The ligand triethylphosphine (PEt₃) or P(CH₂CH₃)₃ is a monodentate ligand. It was found that NiCl₂(PEt₃)₂ is diamagnetic, while Ni(NO₃)₂(PEt₃)₂ is paramagnetic. Determine which of the two complexes is tetrahedral and which is square planar.

Draw the orbital diagram for the unbonded metal ion and the metal ion in the tetrahedral complex [Cu(CN)₄]^2–. What is the hybridization used for bonding? How many unpaired electrons are present in the complex?

Describe the bonding in [Zn(CO)₂]²⁺ using the valence bond theory. Draw the orbital diagrams for both the free and complex metal ions. Find out how many unpaired electrons there are and which hybrid orbital is utilized to form the bonds in the complex.