Which statements about mercury are correct?

Options

A. Hg is a liquid metal
B. Hg forms two series of salts
C. Hg forms no amalgam with iron and platinum
D. Hg does not show variable valency

Answer

To determine which statements about mercury are correct, let's analyze the properties and characteristics of mercury (Hg) step by step.

### Step-by-Step Solution:

1. **Identify the Atomic Number and Symbol**:
- Mercury has an atomic number of 80 and is represented by the symbol Hg.

2. **State the Physical Form**:
- Mercury is unique among metals as it is the only metal that is liquid at room temperature. This property makes it useful in thermometers.

3. **Determine Oxidation States**:
- Mercury can exhibit two oxidation states: +1 and +2. This means it can form compounds where it has lost one or two electrons.

4. **Electronic Configuration**:
- The electronic configuration of mercury is [Xe] 4f14 5d10 6s2.
- When it loses one electron to form Hg+, it becomes [Xe] 4f14 5d10 6s1.
- When it loses two electrons to form Hg2+, it becomes [Xe] 4f14 5d10.

5. **Stability of the d-Orbitals**:
- The fully filled d-orbitals (5d10) in mercury contribute to its stability, which is why it does not typically exhibit a +3 oxidation state. The stability of the d10 configuration prevents the loss of additional electrons.

6. **Formation of Amalgams**:
- Mercury can form amalgams with most metals, which are alloys of mercury with other metals. However, it does not form amalgams with iron and platinum.

7. **Variable Oxidation States**:
- Although mercury can show +1 and +2 oxidation states, it does not exhibit variable valency in the same way that some other transition metals do. Therefore, it is not considered to have variable oxidation states.

### Conclusion:
Based on the analysis:
- Mercury is a transition metal with atomic number 80 (correct).
- It is liquid at room temperature (correct).
- It forms two oxidation states: +1 and +2 (correct).
- It forms amalgams with most metals except iron and platinum (correct).
- It does not exhibit variable valency (correct).

Thus, all statements about mercury are correct.