Which of the following statements is true regarding ionic size?

Options

A. More the positive charge on a cation greater its size
B. More the negative charge on an anion smaller its size
C. Cations are always smaller than their neutral atom
D. Anions are always smaller than their neutral atom

Answer

To determine which statement regarding ionic size is true, we need to analyze the provided statements based on the concepts of cations and anions, effective nuclear charge, and ionic size.

### Step-by-Step Solution:

1. **Understanding Cations and Anions**:
- Cations are positively charged ions formed when an atom loses one or more electrons.
- Anions are negatively charged ions formed when an atom gains one or more electrons.

2. **Effect of Charge on Ionic Size**:
- When a cation is formed (e.g., A to A+), the number of electrons decreases. This leads to a reduction in electron-electron repulsion and an increase in effective nuclear charge felt by the remaining electrons. As a result, the electrons are pulled closer to the nucleus, causing the cation to be smaller than the neutral atom.
- Conversely, when an anion is formed (e.g., A to A-), the addition of electrons increases electron-electron repulsion and decreases the effective nuclear charge felt by the outer electrons. This leads to an increase in size, making the anion larger than the neutral atom.

3. **Analyzing the Statements**:
- **Statement A**: "More the positive charge on a cation, greater its size."
- This is **false**. More positive charge means more protons relative to electrons, leading to a smaller ionic size.
- **Statement B**: "More the negative charge on an anion, smaller its size."
- This is **false**. More negative charge means more electrons, which increases the size of the anion.
- **Statement C**: "Cations are always smaller than their neutral atom."
- This is **true**. Cations are indeed smaller than their neutral atoms due to the reasons explained above.

4. **Conclusion**:
- The correct statement regarding ionic size is **C**: "Cations are always smaller than their neutral atom."

### Final Answer:
**C. Cations are always smaller than their neutral atom.**