1. Diagonal relationship is shown by elements of?
+
Correct Answer
Li–Mg, Be–Al and B–Si
What is a Diagonal Relationship?
A diagonal relationship is the similarity in properties
between certain elements that are placed diagonally adjacent to each other
in the periodic table.
The important diagonal pairs are:
Li ↘ Mg
Be ↘ Al
B ↘ Si
These relationships are especially noticeable among elements of the
2nd and 3rd periods.
Be ↘ Al
B ↘ Si
Why Does It Occur?
Moving diagonally downward and to the right causes two opposing trends:
Moving down: atomic size and shielding increase.
Moving right: atomic size decreases and effective nuclear charge increases. These effects partially compensate each other along a diagonal, so the elements can have similar:
Moving down: atomic size and shielding increase.
Moving right: atomic size decreases and effective nuclear charge increases. These effects partially compensate each other along a diagonal, so the elements can have similar:
Atomic size + Charge density + Polarising power
Consequently, some chemical properties become similar.
Examples
1. Lithium and Magnesium
- Both form nitrides.
- Both form relatively less soluble carbonates.
- Both form nitrates that decompose on heating to oxides.
- Both show amphoteric oxides and hydroxides.
- Both form covalent compounds more readily than expected for their groups.
- Both form complexes due to their relatively high charge density.
- Both are hard, high-melting metalloids.
- Both form acidic oxides.
- Both show predominantly covalent bonding.
JEE / NEET Shortcut
Remember: Li–Mg, Be–Al, B–Si
A useful memory sequence is:
Li → Mg
Be → Al
B → Si
The most commonly asked diagonal relationship is
Li and Mg.
Be → Al
B → Si
30 Related MCQs with Solutions
1. Diagonal relationship is shown by:
A. Li and Mg
B. Na and Mg
C. K and Ca
D. Li and Be
Answer: A. Li and Mg
2. Which is a correct diagonal pair?
A. Be–Al
B. Be–Mg
C. B–Al
D. C–Al
Answer: A. Be–Al
3. The third important diagonal pair is:
A. C–Al
B. B–Si
C. N–P
D. O–S
Answer: B. B–Si
4. Diagonal relationship occurs mainly between elements of:
A. 1st and 2nd periods
B. 2nd and 3rd periods
C. 4th and 5th periods only
D. Lanthanides only
Answer: B
5. Which pair has amphoteric oxides and shows diagonal relationship?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–Ca
Answer: B. Be–Al
6. Which pair is known for similar carbonate behaviour?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–Al
Answer: A. Li–Mg
7. Which pair contains metalloids with similar covalent character?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–Al
Answer: C. B–Si
8. Diagonal relationship arises because:
A. All properties become identical
B. Opposing periodic trends partially compensate
C. Atomic number becomes constant
D. All atoms have the same radius
Answer: B
9. Which element is diagonally related to Li?
A. Be
B. Mg
C. Na
D. Ca
Answer: B. Mg
10. Which element is diagonally related to Be?
A. Mg
B. Al
C. Si
D. Na
Answer: B. Al
11. Which element is diagonally related to B?
A. Al
B. Si
C. P
D. Mg
Answer: B. Si
12. Li and Mg belong to:
A. Same group
B. Same period
C. Diagonally related positions
D. Same block only
Answer: C
13. BeO and Al2O3 are similar because both are:
A. Strongly acidic
B. Amphoteric
C. Strongly basic
D. Neutral
Answer: B. Amphoteric
14. Which pair shows diagonal similarity in oxide nature?
A. Be–Al
B. Na–Mg
C. K–Ca
D. F–Cl
Answer: A. Be–Al
15. Which pair is NOT a standard diagonal relationship?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–Ca
Answer: D. Na–Ca
16. Diagonal relationship is most prominent in:
A. s-block and p-block elements of early periods
B. Noble gases only
C. Transition metals only
D. Lanthanides only
Answer: A
17. Which factor is important in diagonal similarity?
A. Similar charge density
B. Same atomic number
C. Same number of shells
D. Same mass number
Answer: A
18. Li and Mg have similarity partly because of:
A. Comparable charge density of their ions
B. Same group number
C. Same atomic number
D. Same period
Answer: A
19. Which pair forms predominantly covalent compounds?
A. Be–Al
B. Na–K
C. K–Rb
D. Cs–Ba
Answer: A. Be–Al
20. Boron and silicon are both generally classified as:
A. Noble gases
B. Metalloids
C. Alkali metals
D. Alkaline earth metals
Answer: B. Metalloids
21. Which pair has similar amphoteric behaviour?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–K
Answer: B. Be–Al
22. Which pair shows similarity in nitride formation?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–Al
Answer: A. Li–Mg
23. Diagonal relationship is caused partly by similar:
A. Polarising power
B. Atomic numbers
C. Mass numbers
D. Nuclear composition
Answer: A. Polarising power
24. Which pair has acidic oxides and a diagonal relationship?
A. B–Si
B. Li–Mg
C. Be–Al
D. Na–Mg
Answer: A. B–Si
25. The diagonal relationship is best represented as:
A. Horizontal similarity
B. Vertical similarity
C. Diagonal similarity
D. Random similarity
Answer: C. Diagonal similarity
26. Which pair is diagonally related?
A. Li–Mg
B. Na–Mg
C. Mg–Al
D. Al–Si
Answer: A. Li–Mg
27. Which of the following is the standard set of diagonal pairs?
A. Li–Mg, Be–Al, B–Si
B. Na–Mg, Mg–Al, Al–Si
C. F–Cl, Cl–Br, Br–I
D. Na–K, Mg–Ca, Al–Ga
Answer: A
28. Which pair shows the strongest commonly discussed diagonal relationship?
A. Li–Mg
B. Be–Al
C. B–Si
D. Na–Ca
Answer: A. Li–Mg
29. Diagonal relationship is related to the balance between:
A. Atomic size and effective nuclear attraction
B. Mass and density only
C. Neutrons and isotopes only
D. Melting and boiling points only
Answer: A
30. Which statement is correct?
A. Li–Mg, Be–Al and B–Si show diagonal relationships
B. Li–Na and Be–Mg are diagonal pairs
C. F–Cl is a diagonal pair
D. Na–K is a diagonal pair
Answer: A
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