Final answer:
The blue compound formed by adding trimethylphosphine to a solution of nickel(II) chloride has the molecular formula NiCl2(P(CH3)3)2 and an octahedral geometry. The complex [Co(en)3]Cl3 has zero unpaired electrons and no isomers. The compound Mg3[Cr(CN)6]2 is paramagnetic, and salts of the gold(I) ion, Au*, are generally colorless.
Step-by-step explanation:
Geometry and Molecular Formula of the Blue Compound:
The blue compound formed by adding trimethylphosphine to a solution of nickel(II) chloride is a coordination compound. The molecular formula of this compound is NiCl2(P(CH3)3)2 and the geometry is octahedral. This means that the nickel atom is surrounded by 6 ligands arranged in an octahedral shape.
Unpaired Electrons in [Co(en)3]Cl3:
The complex [Co(en)3]Cl3 is a coordination compound as well. The cobalt atom in this complex has a d⁶ electron configuration, which means it has zero unpaired electrons. Additionally, this complex does not have any isomeric forms.
Paramagnetism or Diamagnetism in Mg3[Cr(CN)6]2:
Mg3[Cr(CN)6]2 is a coordination compound with a formula containing chromium(III) ions surrounded by cyanide ligands. Due to the presence of unpaired d electrons in the chromium atom, this compound is paramagnetic. Paramagnetic compounds are attracted to magnetic fields. In contrast, diamagnetic compounds have all paired electrons and are not attracted to magnetic fields.
Color of Salts of Gold(I) Ion:
Salts of the gold(I) ion, Au*, are generally colorless. This is because the gold(I) ion only has a single d-electron and its absorption of visible light is weak, resulting in no significant color.
Crystal Field Splitting and Energy Absorption of [CuCl4]² and [Cu(H₂O)6]²+:
[CuCl4]² is green and [Cu(H₂O)6]²+ is blue. The [Cu(H₂O)6]²+ complex absorbs higher-energy photons compared to the [CuCl4]² complex. This is because water molecules are stronger ligands than chloride ions. Stronger ligands cause a larger crystal field splitting, which results in the absorption of higher-energy photons.