The size of the species, `Pb,Pb^(2+), Pb^(4+)` decreases as -

Options

A. `Pb^(4+) gt Pb^(2+) gt Pb`
B. `Pb gt Pb^(2+) gt Pb^(4+)`
C. `Pb gt Pb^(4+) gt Pb^(2+)`
D. `Pb^(4+) gt Pb gt Pb^(2+)`

Answer

To determine the size of the species Pb, Pb²⁺, and Pb⁴⁺, we need to analyze how the charge on the lead ion affects its ionic size.

### Step-by-Step Solution:

1. **Identify the Neutral Atom Size**:
- The size of the neutral lead atom (Pb) is the largest among the three species. This is because it has the most electrons, which are repelling each other and causing the atom to be larger.

2. **Understand Ion Formation**:
- When lead loses electrons to form cations, it becomes smaller. The formation of Pb²⁺ involves the loss of two electrons, and Pb⁴⁺ involves the loss of four electrons.

3. **Effect of Charge on Size**:
- The more positive the charge on a cation, the smaller its size. This is due to the increased effective nuclear charge (Z_eff) experienced by the remaining electrons.
- For Pb²⁺, there are still three valence electrons left, while for Pb⁴⁺, only one valence electron remains.

4. **Analyze Effective Nuclear Charge**:
- In Pb, all five outer electrons experience the nuclear charge from the nucleus. In Pb²⁺, three electrons experience the same nuclear charge, and in Pb⁴⁺, only one electron feels the nuclear charge.
- As the number of outer shell electrons decreases, the effective nuclear charge felt by each electron increases, pulling the electrons closer to the nucleus and resulting in a smaller ionic size.

5. **Conclusion**:
- Therefore, the order of size from largest to smallest is: Pb > Pb²⁺ > Pb⁴⁺.

### Final Answer:
The size of the species decreases in the order:
**Pb > Pb²⁺ > Pb⁴⁺**.