Question

Is a complex with the same number of unpaired electrons as the free gaseous metal ion termed high spin or low spin?

Short answer

The complex with the same number of unpaired electrons as the free metal ion is termed a high-spin complex.

Step-by-step solution

The concept of magnetic properties is used

The magnetic properties of metal complexes rise from the energy splitting of metal ion's dorbitals and these magnetic properties are based on the number of unpaired electrons in dorbitals

Detailed explanation

The complex with the same number of unpaired electrons as the free metal ion is termed a high-spin complex.

The magnetic properties of metal complexes rise from the energy splitting of metal ion's d orbitals and these magnetic properties are based on the number of unpaired electrons in d orbitals. The occupancy of d orbitals depends on pairing energy $\left({\mathrm{E}}_{\mathrm{pairing}}\right)$and crystal field splitting energy $\left(\Delta \right)$. The complex with the same number of unpaired electrons as the free metal ion is termed as high-spin complex and it has the maximum number of unpaired electrons. High-spin complexes occur when weak-field ligands bond with central metal ion because they cause small splitting energy; in this case ${\mathrm{E}}_{\mathrm{pairing}}>∆$.