Which one of the following statements are true?
(1) Transition metals from alloys
(2) Transition metals form complexes
(3) `Zn, Cd and Hg` are transition metals
(4) `K_(2)[PtCl_(6)]` is a well known compound, but corresponding nickel compound is not known.

Options

A. 1, 2
B. 2, 4
C. 1, 2, 4
D. 2, 3, 4

Answer

To determine which statements about transition metals are true, let's analyze each statement step by step.

### Step 1: Analyze Statement 1
**Statement 1:** Transition metals form alloys.

- **Explanation:** Transition metals have similar atomic sizes and can easily replace each other in a crystal lattice. This property allows them to form alloys with one another.

**Conclusion:** This statement is **true**.

### Step 2: Analyze Statement 2
**Statement 2:** Transition metals form complexes.

- **Explanation:** Transition metals can form complexes because they can exist as small, highly charged cations. They have vacant d-orbitals that can accept electron pairs from ligands, allowing for complex formation.

**Conclusion:** This statement is **true**.

### Step 3: Analyze Statement 3
**Statement 3:** Zn, Cd, and Hg are transition metals.

- **Explanation:** Transition metals are defined as elements that have an incomplete d-subshell in any of their oxidation states. Zinc (Zn), Cadmium (Cd), and Mercury (Hg) have a full d-subshell (d10 configuration) in their most stable oxidation states and do not meet the criteria for transition metals.

**Conclusion:** This statement is **false**.

### Step 4: Analyze Statement 4
**Statement 4:** K₂[PtCl₆] is a well-known compound, but the corresponding nickel compound is not known.

- **Explanation:** The stability of compounds is influenced by the ionization energies of the metals involved. Platinum has lower first four ionization energies compared to nickel, which allows for the formation of stable compounds like K₂[PtCl₆]. In contrast, nickel does not form a stable corresponding compound.

**Conclusion:** This statement is **true**.

### Final Conclusion
Based on the analysis:
- Statement 1: True
- Statement 2: True
- Statement 3: False
- Statement 4: True

Thus, the true statements are 1, 2, and 4.