The average life period of a radioactive element is the reciprocal of its

Options

A. Half-life period
B. Disintegration constant
C. Number of atoms present at any time
D. Number of neutrons

Explanation

To solve the question regarding the average life period of a radioactive element, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Average Life Period**: The average life period (also known as the mean life) of a radioactive element is denoted as \( T_{average} \).

2. **Relationship with Decay Constant**: The average life period is mathematically defined as the reciprocal of the decay constant (\( \lambda \)). This can be expressed as:
\[ T_{average} = \frac{1}{\lambda} \]

3. **Defining Decay Constant**: The decay constant (\( \lambda \)) is a measure of the probability of decay of a radioactive atom per unit time. It is similar to the rate constant in first-order reactions and has units of time inverse (e.g., seconds\(^{-1}\)).

4. **Units of Average Life Period**: Since \( \lambda \) has units of time\(^{-1}\), when we take the reciprocal, the units of \( T_{average} \) will be in time (e.g., seconds).

5. **Conclusion**: Therefore, the average life period of a radioactive element is the reciprocal of its decay constant (\( \lambda \)), and it can be expressed as:
\[ T_{average} = \frac{1}{\lambda} \]

### Final Answer:
The average life period of a radioactive element is the reciprocal of its decay constant (\( \lambda \)).

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