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, let’s analyze each option step by step.

### Step 1: Understanding Ionic Size
Ionic size refers to the size of ions, which can be either cations (positively charged ions) or anions (negatively charged ions). The size of an ion is influenced by the number of protons and electrons it has.

### Step 2: Analyzing Cations
- **Cations** are formed when an atom loses one or more electrons.
- When an electron is removed, the number of protons remains the same, but the number of electrons decreases.
- This leads to a higher effective nuclear charge (the net positive charge experienced by electrons), which pulls the remaining electrons closer to the nucleus, resulting in a smaller ionic size.
- **Conclusion**: Cations are always smaller than their neutral atoms.

### Step 3: Analyzing Anions
- **Anions** are formed when an atom gains one or more electrons.
- When an electron is added, the number of protons remains the same, but the number of electrons increases.
- This results in a lower effective nuclear charge because the protons are now attracting more electrons than before, leading to increased electron-electron repulsion and a larger ionic size.
- **Conclusion**: Anions are always larger than their neutral atoms.

### Step 4: Evaluating the Statements
Now, let's evaluate the given statements:

1. **More positive charge on cation, greater its size**: This is false. More positive charge means a stronger attraction to electrons, leading to a smaller size.

2. **More negative charge on anion, smaller its size**: This is false. More negative charge means more electrons, leading to a larger size.

3. **Cations are always smaller than their neutral form**: This is true. As explained, losing electrons leads to a smaller ionic size.

4. **Anions are smaller than their neutral form**: This is false. Gaining electrons leads to a larger ionic size.

### Conclusion
The only true statement regarding ionic size is:
**Cations are always smaller than their neutral form.**