Coordination Compounds

Step 1: Understanding bidentate ligands.
Bidentate ligands contain two donor atoms which can attach to a central metal ion, forming two coordinate bonds simultaneously.
Step 2: Analysis of options.
(A) E.D.T.A: This is a hexadentate ligand (can donate six pairs of electrons), not just bidentate.
(B) Ethylene diamine: Correct — It has two groups, each donating a lone pair, making it bidentate.
(C) Acetate ion: Monodentate, binds through one oxygen atom.
(D) Pyridine: Monodentate, binds through nitrogen only.
Step 3: Conclusion.
Thus, the correct answer is (B) Ethylene diamine.

Step 1: Assign charges to ligands.
- Ethylene (C H ) is a neutral ligand.
- Chloride (Cl ) has charge . There are 3 chlorides, so total = .
Step 2: Apply oxidation number rule.
Let the oxidation number of Pt be . The overall charge is . Step 3: Conclusion.
The oxidation number of Pt in [Pt(C H )Cl ] is +2.

Step 1: Recall the rule for paramagnetism.
A species is paramagnetic if it has one or more unpaired electrons; otherwise, it is diamagnetic.
Step 2: Write d–electron configurations.
Ag : (all paired) diamagnetic.
Cu : (one unpaired) paramagnetic.
Zn : (all paired) diamagnetic.
Au : (all paired) diamagnetic.
Step 3: Conclusion.
Only Cu has an unpaired electron; hence it is paramagnetic.

Step 1: Definition of Double Salt.
A double salt is formed by the combination of two simple salts in a definite proportion that crystallize together. In aqueous solution, it completely dissociates into its constituent ions.
Step 2: Definition of Complex Salt.
A complex salt consists of a central metal ion bonded to one or more ligands. It does not dissociate completely in water but gives a complex ion.
Step 3: Example.
- Double Salt: dissociates completely into and .
- Complex Salt: does not dissociate completely; it gives complex ion .
Step 4: Key Difference Table.
\begin{tabular}{|p{4cm}|p{5cm}|} \hline Double Salt & Complex Salt
\hline Completely dissociates in water & Partially dissociates, forms complex ion
\hline Exists only in solid state & Exists in solution as complex ions
\hline Example: Mohr's salt & Example: Potassium ferrocyanide
\hline \end{tabular}

Step 1: Historical background.
The first important theory of coordination compounds was given by Alfred Werner in 1893. He proposed the idea of primary valency (ionisable) and secondary valency (non-ionisable) to explain coordination complexes.
Step 2: Analysis of options.
(A) Slater: Known for Slater’s rules in atomic structure, not coordination compounds.
(B) Pauling: Contributed valence bond theory, but not the first to explain complexes.
(C) Werner: Correct — He introduced the first scientific theory of coordination compounds.
(D) Lewis: Proposed Lewis acid-base concept, unrelated here.
Step 3: Conclusion.
Therefore, the correct answer is (C) Werner.

Step 1: Understanding coordination number.
The coordination number of a metal ion is the number of ligand atoms bonded to it. In , each oxalate ion ( ) is a bidentate ligand, meaning it bonds through two donor atoms. With three bidentate ligands, the coordination number of Ni is 6. Step 2: Analysis of options.
(A) 3: This is incorrect; the coordination number is higher.
(B) 6: Correct — The coordination number of Ni in is 6 because each oxalate ion is bidentate.
(C) 4: This is incorrect; the complex contains three bidentate ligands, giving a coordination number of 6.
(D) 5: This is incorrect; a coordination number of 5 is not typical for this complex.
Step 3: Conclusion.
The correct answer is (B) because each oxalate ligand bonds with two donor atoms, leading to a coordination number of 6.