Elements of which block generally show maximum variation in valency?

Options

A. p-block elements
B. s-block elements
C. d-block elements
D. d and s-block elements

Answer

To determine which block of elements generally shows the maximum variation in valency, we can analyze the characteristics of the different blocks in the periodic table: S block, P block, D block, and F block.

### Step-by-Step Solution:

1. **Understanding Valency**:
- Valency refers to the ability of an element to combine with other elements, which is determined by the number of electrons in its outermost shell. Elements can exhibit different valencies depending on how many electrons they lose, gain, or share during chemical reactions.

2. **Identifying the Blocks**:
- The periodic table is divided into four main blocks based on the electron configuration of the elements:
- **S block**: Groups 1 and 2 (alkali and alkaline earth metals).
- **P block**: Groups 13 to 18 (includes nonmetals, metalloids, and some metals).
- **D block**: Transition metals (Groups 3 to 12).
- **F block**: Lanthanides and actinides.

3. **Analyzing Valency in Each Block**:
- **S block**: Elements typically show a valency of +1 or +2 (e.g., Na can be +1, Mg can be +2).
- **P block**: Elements can show multiple valencies, but they are generally less variable than those in the D block.
- **D block**: Transition metals are known for their ability to exhibit multiple oxidation states due to the presence of d electrons. For example, manganese (Mn) can have valencies of +2, +4, +6, and +7.
- **F block**: These elements also show variable valency, but they are less common in everyday chemistry compared to transition metals.

4. **Conclusion**:
- Among all the blocks, the D block elements (transition metals) show the maximum variation in valency. This is primarily due to the involvement of d electrons in bonding, allowing for a range of oxidation states.

### Final Answer:
The elements of the **D block** generally show maximum variation in valency.