Question

Which among the following is a paramagnetic complex?
[NEET Kar. 2013]
(a) Mo(CO)₆ (b) [Co(NH₃)₆]³⁺
(c) [Pt(en)Cl₂] (d) [CoBr₄]²⁻
(At. No. of Mo = 42, Pt = 78)

Answer 1

Answer:

OPTION D IS A CORRECT ANSWER

Explanation:

1. (Co 2 + ) = (3d5)
2. bromine is a weak atom  it have tetrahedral structure
3. it has  5 unpaired electron pair in its d orbital
4. it has high spin
5. other compounds have nature diamagenetic and low spilliting power
6. more the unpaired electron more the paramagnetic nature
7. out of given compound  Br have more unpaired electron pairs so it is correct option

Answer 2

The paramagnetic complex is :

(d) [CoBr₄]²⁻

• The electronic configuration of Co²⁺ is 3d⁵.

• Bromine has a tetrahedral structure and is weak.

• The d orbital of Bromine consists of unpaired electrons that are 5 in number.
• Since the paramagnetism depends upon the number of unpaired electrons present.

• [CoBr₄]²⁻ is paramagnetic in nature due to the presence of  more number of unpaired electrons in comparison to other given complexes.

• The rest of the given compounds are diamagnetic as they don't have any unpaired electrons in their d orbitals.