Answer:
See explanation
Step-by-step explanation:
Whether a ligand is strong or weak highly depends on its position in the spectrochemical series. Ligands that are found towards the left hand side of the series are weak field ligands while ions that occur towards the right hand side of the series are strong field ligands. The spectrochemical series is an arrangement of ligands in order of increasing magnitude of crystal field splitting.
Most of the strong field ligands have strong pi bonds and are capable producing greater crystal field splitting.
NH3, an and NO2 are all strong field ligands hence they produce long wavelengths and lead to the formation of diamagnetic complexes.