Cause of diagonal relationship is

Options

A. Similar electronic configuration of the elements
B. Similar e/r ratio of the elements
C. Same number of valency electrons in the elements
D. Same atomic weights of the elements

Answer

### Step-by-Step Solution:

1. **Understanding Diagonal Relationship**: The diagonal relationship in the periodic table refers to the similarities in properties between certain pairs of elements that are not in the same group but are positioned diagonally to each other. For example, lithium (Li) and magnesium (Mg) show similarities in their chemical behavior.

2. **Identifying Causes of Diagonal Relationship**: The diagonal relationship arises due to several factors, but the most significant one is the similarity in their charge-to-size ratio.

3. **Charge-to-Size Ratio (E/R Ratio)**: The charge-to-size ratio (E/R ratio) is defined as the effective charge (E) of an ion divided by its radius (R). Elements that have similar charge-to-size ratios tend to exhibit similar properties.

4. **Similar Electronic Configuration**: Elements that are diagonally related often have similar electronic configurations, particularly in their valence shells. This similarity contributes to their comparable chemical properties.

5. **Valence Electrons**: Elements that are diagonally related usually have the same number of valence electrons, which plays a crucial role in determining their reactivity and bonding behavior.

6. **Atomic Weight**: While atomic weight can also be a factor, it is not the primary cause of the diagonal relationship. The focus should be on the charge-to-size ratio and electronic configuration.

7. **Conclusion**: The diagonal relationship is primarily caused by the similar charge-to-size ratio (E/R ratio) of the elements involved. This similarity leads to comparable chemical and physical properties.

### Final Answer:
The cause of the diagonal relationship is the similar charge-to-size ratio (E/R ratio) of the elements.

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