Assertion Coordination compounds are generally formed by transition metals
Reason Transition metals generally have partly filled d-orbitals of the nth shell .

Options

A. If both `(A)` and ` (R )` are correct and `(R )` is the correct explanation of `(A ) ` .
B. If both `(A)` and ` (R )` are correct and `(R )` is the correct explanation of `(A ) ` .
C. If`(A)` is correct, but `( R )` is incorrect .
D. Both `(A)` and `(R ) ` are incorrect .

Explanation

To analyze the assertion and reason provided in the question, we can break it down into a step-by-step solution.

### Step 1: Understand the Assertion
The assertion states that "Coordination compounds are generally formed by transition metals."

**Hint:** Recall the definition of coordination compounds and identify the role of transition metals in their formation.

### Step 2: Analyze the Reason
The reason states that "Transition metals generally have partly filled d-orbitals of the nth shell."

**Hint:** Consider the electronic configuration of transition metals and how it relates to their d-orbitals.

### Step 3: Define Coordination Compounds
Coordination compounds are formed when a central metal atom (often a transition metal) is surrounded by molecules or ions known as ligands, which donate electron pairs to the metal.

**Hint:** Remember the characteristics of ligands and how they interact with the central metal atom.

### Step 4: Identify Characteristics of Transition Metals
Transition metals are known for having:
- Partially filled d-orbitals.
- The ability to exhibit multiple oxidation states.
- The presence of vacant orbitals that can accept electron pairs from ligands.

**Hint:** Review the periodic table and the properties of d-block elements.

### Step 5: Confirm the Assertion
Since coordination compounds are indeed formed by transition metals due to their ability to accept electron pairs and their suitable electronic configurations, the assertion is correct.

**Hint:** Think of examples of coordination compounds formed by transition metals, such as [Fe(CN)6]²⁻ and [Cu(NH3)4]²⁺.

### Step 6: Evaluate the Reason
The reason mentions "partly filled d-orbitals of the nth shell." However, the correct terminology should refer to the (n-1)d orbitals being partially filled, as the d-orbitals belong to the previous shell.

**Hint:** Clarify the difference between the nth shell and the (n-1)th shell in the context of transition metals.

### Step 7: Conclusion
Based on the analysis:
- The assertion is **correct**.
- The reason is **incorrect** because it misidentifies the shell of the d-orbitals.

Thus, the correct answer is that the assertion is true, but the reason is false.

**Final Answer:** Option C (Assertion is true, Reason is false).