Question

The number of following pairs of elements which exhibit diagonal relationship is:

• i. B & Si
• ii. Be & Al
• iii. Li & Mg
• iv. Al & S

• A. 2
• B. 1
• C. 3
• D. 4

Hint:

Diagonal Relationship: Similarities between certain diagonally placed elements arise due to comparable electronegativity and ionic size. Most common between Period 2 and Period 3.

Answer 1

The Correct Option is C

Diagonal relationships occur between elements diagonally adjacent in periods 2 and 3. Known pairs:

• \( \mathrm{Li} \) and \( \mathrm{Mg} \)
• \( \mathrm{Be} \) and \( \mathrm{Al} \)
• \( \mathrm{B} \) and \( \mathrm{Si} \)

These pairs share similar charge-to-radius ratios and chemical properties.

Examine the pairs:

• (i) \( \mathrm{B} \) & \( \mathrm{Si} \) → Yes, known diagonal pair
• (ii) \( \mathrm{Be} \) & \( \mathrm{Al} \) → Yes, known diagonal pair
• (iii) \( \mathrm{Li} \) & \( \mathrm{Mg} \) → Yes, known diagonal pair
• (iv) \( \mathrm{Al} \) & \( \mathrm{S} \) → No, both are in the same period and not diagonally related

So, total correct diagonal pairs: 3.

Answer 2

Step 1: Understand the concept of diagonal relationship
Diagonal relationship occurs between certain pairs of elements in the second and third periods of the periodic table where they show similar chemical properties despite being in different groups. This typically happens between elements diagonally adjacent in the periodic table.

Step 2: Analyze each pair
i. B (Group 13, Period 2) & Si (Group 14, Period 3)
- These elements exhibit diagonal relationship due to similar size and chemical behavior.

ii. Be (Group 2, Period 2) & Al (Group 13, Period 3)
- Be and Al show diagonal relationship as both form amphoteric oxides and similar compounds.

iii. Li (Group 1, Period 2) & Mg (Group 2, Period 3)
- Li and Mg exhibit diagonal relationship with similarities in ionic sizes and chemical behavior.

iv. Al (Group 13, Period 3) & S (Group 16, Period 3)
- Al and S are not diagonally related; they belong to different periods and groups without typical diagonal similarities.

Step 3: Count the pairs exhibiting diagonal relationship
Pairs i, ii, and iii exhibit diagonal relationships.
Pair iv does not.

Step 4: Conclusion
The number of pairs exhibiting diagonal relationship is 3.