Among the following, the compound that has the maximum coordination number is/are:

1. [Co(NH₃)₆]³⁺
2. [Cr(C₂O₄)₃]^3-
3. [CoCl₃(H₂O)₃]
4. All of the above have the same coordination number

The complex ion among the following that cannot absorb visible light is:

1. [Ni(CN)₄]^2-

2. [Cr(NH₃)₆]³⁺

3. [Fe(H₂O)₆]²⁺

4. [Ni(H₂O)₆]²⁺

The most stable complex among the following species is:

1.  $\left[\mathrm{Fe}{\left(\mathrm{CO}\right)}_5\right]$

2.  $[\mathrm{Fe}{\left(\mathrm{CN}\right)}_6{]}^{3-}$

3.  $[\mathrm{Fe}{\left({\mathrm{C}}_2{\mathrm{O}}_4\right)}_3{]}^{3-}$

4.  $[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6{]}^{3+}$

[Fe(H₂O)₆]³⁺ and [Fe(CN)₆]^3- differ in:

1. Magnetic nature

2. Oxidation number

3. Co-ordination number

4. Structure

The isomerism displayed by K₃[Co(NO₂)₆] and K₃[Co(ONO)₆] is: 

The geometry and magnetic properties of [NiCl₄]^2-, respectively, are : 

1. Tetrahedral, Paramagnetic

2. Tetrahedral, Diamagnetic

3. Square planar, Paramagnetic

4. Square planar, Diamagnetic  

For a tetrahedral complex [MCl₄]^2-, the spin-only magnetic moment is 3.83 B.M. The element M is:

1. Co

2. Cu

3. Mn

4. Fe

The complex that can exhibit linkage isomerism is:

A person with osteoporosis is also experiencing lead poisoning, and ethylenediamine tetraacetic acid (EDTA) is prescribed for treatment. Which form of EDTA is most suitable for this administration?

1. EDTA

2. Tetrasodium salt

3. Disodium salt

4. Calcium dihydrogen salt