A heavier element containously emits `alpha`-and `beta`-particles. The finally stable element may belong to:
a. 14th group b. 16th group
c. 10th group d. 12 th group

Options

A. a. 14th group
B. b. 16th group
C. c. 10th group
D. d. 12 th group

Explanation

To solve the question, we need to analyze the behavior of heavier elements that emit alpha and beta particles and determine the stable end product of their decay series.

### Step-by-Step Solution:

1. **Understanding Alpha and Beta Emission**:
- Heavier elements tend to be unstable and undergo radioactive decay. This decay can involve the emission of alpha particles (which consist of 2 protons and 2 neutrons) and beta particles (which are high-energy, high-speed electrons or positrons).

2. **Identifying Decay Series**:
- There are four main decay series for heavy elements:
- **4n Series**: Thorium series
- **4n + 1 Series**: Neptunium series
- **4n + 2 Series**: Uranium series
- **4n + 3 Series**: Actinium series

3. **Finding the End Products**:
- Each series has a stable end product:
- **4n Series (Thorium)**: Ends in Lead (Pb) with atomic mass 208 and atomic number 82 (Group 14).
- **4n + 1 Series (Neptunium)**: Ends in Bismuth (Bi) with atomic mass 209 and atomic number 83 (Group 15).
- **4n + 2 Series (Uranium)**: Ends in Lead (Pb) with atomic mass 206 and atomic number 82 (Group 14).
- **4n + 3 Series (Actinium)**: Ends in Lead (Pb) with atomic mass 207 and atomic number 82 (Group 14).

4. **Analyzing the Options**:
- The options provided are:
- a. 14th group
- b. 16th group
- c. 10th group
- d. 12th group
- From the analysis, we see that the stable end products of the decay series (Lead and Bismuth) belong to the 14th group (Lead) and the 15th group (Bismuth).

5. **Conclusion**:
- Since the question asks for the final stable element after continuous alpha and beta emissions, the most likely stable end product belongs to the **14th group**, as Lead is a common end product of several decay series.

### Final Answer:
The finally stable element may belong to **a. 14th group**.