Diagonal Relationship — Li/Mg, Be/Al
s-block Elements
5
JEE Qs
8%
Hard
40
min
Focus on understanding the specific property similarities between Li/Mg and Be/Al and connect them to the similar ionic potential and electronegativity for effective problem-solving.
✅ Key Points for JEE
- 1The diagonal relationship exists between elements of Period 2 and Period 3 (specifically Li/Mg and Be/Al) due to their similar ionic potential (charge/radius ratio) and electronegativity, leading to similar chemical properties.
- 2Lithium and Magnesium both form nitrides (Li3N, Mg3N2) upon direct reaction with nitrogen, form oxides that are less basic than other group members, and their hydroxides are weakly soluble in water.
- 3Beryllium and Aluminium both form covalent compounds, have amphoteric oxides (BeO, Al2O3) and hydroxides (Be(OH)2, Al(OH)3), and dissolve in strong acids and bases.
- 4Both Li and Mg, and Be and Al show similar polarizing power, which contributes to the covalent character of their compounds, differing from the predominantly ionic nature of other group members.
- 5The anomalous behavior of lithium and beryllium within their respective groups is largely explained by their diagonal relationship with magnesium and aluminium, respectively.
⚠️ Common Mistakes
- ✕Memorizing the similarities without understanding the underlying reason (similar ionic potential/electronegativity/polarizing power) makes it difficult to infer properties.
- ✕Confusing the specific sets of similarities between Li/Mg versus Be/Al, leading to incorrect property assignments.
- ✕Failing to recognize the amphoteric nature of Be and Al oxides/hydroxides as a key diagonal similarity.
📝 Practice Questions
See allQ49. List - I List - II Reaction Type of redox reaction (A) Li (I) 589.2 Match List - I with List - II. Choose the correct answer from the options (B) Na (II) 455.5 (C) Rb (III) 670.8 (D) Cs (IV) 780.0 given below : (1) (A)-(II), (B)-(IV), (C)-(III), (D)-(I) (2) (A)-(I), (B)-(IV), (C)-(III), (D)-(II) (3) (A)-(IV), (B)-(II), (C)-(I), (D)-(III) (4) (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
Q40.Ion having highest hydration enthalpy among the given alkaline earth metal ions is: (1) Be2+ (2) Sr2+ (3) Ba2+ (4) Ca2+
Q32.Match List I with List II (A) Slaked lime (I) NaOH (B) Dead burnt plaster (II) Ca ( OH ) 2 (C) Caustic soda (III) Na2CO3 · 10H2O (D) Washing soda (IV) CaSO4 Choose the correct answer form the options given below: (1) (A) - I, (B) - IV, (C) - II, (D) - III (2) (A) - III, (B) - IV, (C) - II, (D) - I (3) (A) - II, (B) - IV, (C) - I, (D) - III (4) (A) - III, (B) - II, (C) -IV, (D) -I
Q33.Choose the correct statement(s): A. Beryllium oxide is purely acidic in nature. B. Beryllium carbonate is kept in the atmosphere of CO2. C. Beryllium sulphate is readily soluble in water. D. Beryllium shows anomalous behavior. Choose the correct answer from the options given below: JEE Main 2023 (01 Feb Shift 1) JEE Main Previous Year Paper (1) A, B and C only (2) B,C and D only (3) A and B only (4) A only
Q40.The correct order of bond enthalpy ( kJ mol–1 ) is: (1) Si −Si > C −C > Sn −Sn > Ge −Ge (2) Si −Si > C −C > Ge −Ge > Sn −Sn (3) C −C > Si −Si > Sn −Sn > Ge −Ge (4) C −C > Si −Si > Ge −Ge > Sn −Sn
Q37. O −O bond length in H2O2 is X than the O −O bond length in F2O2 . The O −H bond length in H2O2 is Y ¯¯ than that of the O −F bond in F2O2 . Choose the correct option for X and Y from the given below. ¯¯ (1) X - shorter, Y− shorter (2) X -shorter, Y -longer (3) X -longer, Y -longer (4) X-longer, Y - shorter
NCERT Chapters
- Class 11 Chemistry Part 2 Ch 10: s-Block Elements