Question

Identify correct pair of properties of [Co(NH₃)₆]³⁺ complex ion.

• A. Low spin, paramagnetic
• B. High spin, diamagnetic
• C. Low spin, diamagnetic
• D. High spin, paramagnetic

Answer 1

The Correct Option is C

Solution:

The complex ion given is [Co(NH₃)₆]³⁺.

Step 1: Determine the oxidation state of cobalt (Co):

Ammonia (NH₃) is a neutral ligand. So, the oxidation state of Co is +3.

Step 2: Electronic configuration of Co³⁺

Atomic number of Co = 27 → Electronic configuration = [Ar] 3d⁷ 4s²
Co³⁺ → [Ar] 3d⁶

Step 3: Nature of ligand and geometry

NH₃ is a strong field ligand (according to the spectrochemical series), which causes pairing of electrons.
This leads to formation of a low spin complex.

Step 4: Magnetism

Due to pairing of electrons in the 3d orbital (caused by the strong ligand NH₃), all electrons are paired in Co³⁺ → no unpaired electrons → diamagnetic

Conclusion: The correct properties are Low spin, Diamagnetic.

Correct Answer: Option 3: Low spin, diamagnetic