Mosley's law relates the frequencies of line X-rays with the following characteristics of the target element

Options

A. its density
B. its atomic weight
C. its atomic number
D. interplaner spacing of the atomic planes

Explanation

To solve the question regarding Moseley's law and its relation to the frequencies of line X-rays with the characteristics of the target element, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Moseley's Law**:
- Moseley's law states that the frequency (ν) of the X-rays emitted by a metal is proportional to the square of its atomic number (Z). The mathematical expression can be written as:
\[ \nu \propto (Z - b)^2 \]
where \( b \) is a constant that depends on the type of X-ray transition.

2. **Identifying the Characteristics of the Target Element**:
- The question asks which characteristic of the target element is related to the frequency of the emitted X-rays. The options provided are:
- Density
- Atomic Weight
- Atomic Number
- Interplanar Spacing of Atomic Planes

3. **Analyzing Each Option**:
- **Density**: This does not directly relate to the frequency of X-rays as per Moseley's law.
- **Atomic Weight**: While atomic weight is related to the mass of the element, it does not influence the frequency of emitted X-rays.
- **Atomic Number**: This is the key characteristic that Moseley's law directly relates to. The frequency of X-rays is proportional to the atomic number.
- **Interplanar Spacing**: This is related to the crystal structure and diffraction but does not directly affect the frequency of X-rays emitted.

4. **Conclusion**:
- Based on the analysis, the characteristic of the target element that Moseley's law relates to the frequency of line X-rays is the **Atomic Number**.

5. **Final Answer**:
- Therefore, the correct answer is **C. Atomic Number**.