In which period or group of periodic table (long form) transition elements are not present? 

Options

A. Third group
B. Third period
C. Twelfth group
D. Thirteenth group

Answer

To determine in which period or group of the periodic table transition elements are not present, we need to understand the definition and placement of transition elements.

### Step-by-Step Solution:

1. **Identify Transition Elements**:
Transition elements are defined as the elements found in the d-block of the periodic table. These include elements from groups 3 to 12.

2. **Examine the Groups**:
- **Third Group**: The third group includes Scandium (Sc), which is a transition element. Therefore, transition elements are present in the third group.
- **Twelfth Group**: The twelfth group includes Zinc (Zn), which is also a transition element. Thus, transition elements are present in the twelfth group as well.
- **Thirteenth Group**: The thirteenth group consists of elements like Boron (B), Aluminium (Al), and Gallium (Ga). None of these are transition elements, as they do not belong to the d-block.

3. **Examine the Periods**:
- **Third Period**: The third period includes elements like Sodium (Na), Magnesium (Mg), and Aluminium (Al). However, it does not include any d-block elements, as the d-block starts from the fourth period. Therefore, there are no transition elements in the third period.
- **Fourth Period**: The fourth period begins with Scandium (Sc) and includes transition elements such as Titanium (Ti), Vanadium (V), and others. Thus, transition elements are present in the fourth period.

4. **Conclusion**:
Based on the analysis, transition elements are not present in the **thirteenth group** and the **third period** of the periodic table.

### Final Answer:
Transition elements are not present in the **third period** and the **thirteenth group** of the periodic table.