S-Block Elements Revision Q&A

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s-Block Elements

Alkali and Alkaline Earth Metals • 110 Short Q&A

Class 11 JEE / NEET

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110 Short Q&A Facts

Part 1: General Properties and Trends
1. Q1: Why are alkali metals highly reactive?
   A: Due to their low ionization energy and tendency to lose their single valence electron to form M⁺ ions easily.
2. Q2: What is the general electronic configuration of alkali metals?
   A: ns¹ where n = 1 to 7 for Li to Cs.
3. Q3: Describe the trend in atomic and ionic radii in alkali metals.
   A: Both atomic and ionic radii increase down the group from Li to Cs.
4. Q4: Why do alkali metals readily lose their outermost electron?
   A: Because of their low ionization enthalpy, making it easy to form stable cations in reactions.
5. Q5: What is the general electronic configuration of alkaline earth metals?
   A: ns², where n = 2 to 7 for Be to Ra.
6. Q6: Describe the trend in ionization energy in alkaline earth metals.
   A: Ionization energy decreases down the group from Be to Ra.
7. Q7: Why do alkali metals have low melting points?
   A: Due to their large atomic size leading to weak metallic bonds.
8. Q8: What is the effect of hydration on the size of alkali metal ions?
   A: Hydration increases the effective ionic radius due to water molecules attached.
9. Q9: How does ionization energy change in alkali metals down the group?
   A: Ionization energy decreases down the group from Li to Cs due to increasing atomic size.
10. Q10: What is the effect of hydration on the atomic size of alkaline earth metals?
    A: Hydration increases the effective size due to water molecules surrounding the ion.
11. Q11: What is the general trend in electronegativity in alkali metals?
    A: Electronegativity decreases down the group.
12. Q12: Why do alkali metals exhibit low density?
    A: Because of their large atomic size and weak metallic bonding.
13. Q13: What causes the increase in ionization energy from sodium to magnesium?
    A: Higher nuclear charge and effective nuclear charge in magnesium.
14. Q14: Which alkali metal has the highest melting point?
    A: Lithium.
15. Q15: Why do alkaline earth metals have higher melting points compared to alkali metals?
    A: Due to their smaller size and higher charge leading to stronger metallic bonding.
16. Q16: What is the electronic configuration of potassium?
    A: [Ar] 4s¹.
17. Q17: How does the atomic radius change from Be to Ba?
    A: Atomic radius increases down the group.
18. Q18: Why is lithium ion smaller than sodium ion?
    A: Because lithium has fewer electron shells and higher effective nuclear charge.
19. Q19: Which group 1 metal is most reactive?
    A: Francium, but practically cesium is the most reactive stable element.
20. Q20: What is the trend in the metallic character of alkaline earth metals?
    A: Metallic character increases down the group.
21. Q21: How is alkali metal ion size affected by hydration?
    A: Hydrated ion size is larger due to water molecules attached.
Part 2: Reactions of s-Block Elements
22. Q22: How do alkali metals react with water? Write a general reaction.
    A: Alkali metals react vigorously with water to form hydroxides and hydrogen gas: 2M + 2H₂O → 2MOH + H₂.
23. Q23: How do alkali metals react with halogens?
    A: They form ionic halides (MX) where M is the metal and X is the halogen.
24. Q24: What is the reducing nature of alkali metals?
    A: Alkali metals are strong reducing agents due to their readiness to lose electrons.
25. Q25: Write the reaction of calcium with water.
    A: Calcium reacts with water slowly to form calcium hydroxide and hydrogen gas: Ca + 2H₂O → Ca(OH)₂ + H₂.
26. Q26: Compare the reactivity of alkali metals and alkaline earth metals with water.
    A: Alkali metals react more vigorously with water than alkaline earth metals.
27. Q27: Which alkaline earth metal is the most reactive?
    A: Barium is the most reactive among alkaline earth metals.
28. Q28: What happens when sodium carbonate is heated strongly?
    A: It decomposes to sodium oxide and carbon dioxide: Na₂CO₃ → Na₂O + CO₂ (on heating).
29. Q29: Write the reaction of sodium metal with liquid ammonia.
    A: Sodium dissolves in liquid ammonia to give a blue solution containing solvated electrons.
30. Q30: How do alkaline earth metals react with acids?
    A: They form salts and hydrogen gas: M + 2HCl → MCl₂ + H₂.
31. Q31: Why are alkali metals stored under kerosene?
    A: To prevent their reaction with moisture and oxygen in air.
32. Q32: Write the reaction of calcium carbonate upon heating.
    A: Calcium carbonate decomposes to calcium oxide and carbon dioxide: CaCO₃ → CaO + CO₂ (with heat).
33. Q33: Why is magnesium less reactive than calcium?
    A: Due to higher ionization energy and stronger metallic bonding in magnesium.
34. Q34: Why do alkali metals have a strong reducing nature?
    A: Due to their low ionization enthalpy and easy loss of the outermost electron.
35. Q35: What happens when sodium reacts with chlorine gas?
    A: Sodium reacts vigorously with chlorine to form sodium chloride (NaCl).
36. Q36: How does the reactivity of alkali metals differ in air?
    A: Lithium forms a nitride, while other alkali metals form oxides or peroxides on exposure to air.
37. Q37: Write the reaction of magnesium with steam.
    A: Mg + H₂O (steam) → MgO + H₂.
38. Q38: What is the reaction of sodium with oxygen at room temperature?
    A: Sodium forms sodium peroxide Na₂O₂.
39. Q39: What is the characteristic flame color of sodium?
    A: Bright yellow flame.
40. Q40: How do alkaline earth metals react with nitrogen?
    A: Some, like calcium and magnesium, form nitrides upon heating.
41. Q41: Write the reaction of calcium hydroxide with carbon dioxide.
    A: Ca(OH)₂ + CO₂ → CaCO₃ + H₂O.
42. Q42: What is the product formed when sodium reacts with dry chlorine gas?
    A: Sodium chloride (NaCl).
43. Q43: What happens when alkali metals react with acids?
    A: They form the corresponding salt and hydrogen gas.
44. Q44: Explain why sodium metal cannot be stored in air.
    A: It reacts rapidly with moisture and oxygen, forming oxides and hydroxides.
45. Q45: What is the reducing agent in metal displacement reactions among s-block metals?
    A: The alkali metals due to their readiness to lose electrons.
46. Q46: Write the reaction of sodium carbonate with hydrochloric acid.
    A: Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O.
47. Q47: What is the characteristic reaction of alkali metals with oxygen?
    A: Formation of oxides, peroxides, or superoxides depending on the metal.
48. Q48: Write the reaction for the formation of sodium hydroxide from sodium metal.
    A: 2Na + 2H₂O → 2NaOH + H₂.
49. Q49: What is the flame color of calcium in flame tests?
    A: Brick red.
50. Q50: What product forms when calcium reacts with nitrogen?
    A: Calcium nitride Ca₃N₂.
51. Q51: What gases are released when calcium carbonate reacts with acids?
    A: Carbon dioxide gas is released.
52. Q52: What happens when calcium hydroxide reacts with excess CO₂?
    A: It forms calcium bicarbonate which is soluble in water.
53. Q53: Why is potassium more reactive than sodium?
    A: Because its valence electron is farther from the nucleus and more easily lost.
54. Q54: What is the reaction of sodium with hydrogen?
    A: Sodium hydride is formed: 2Na + H₂ → 2NaH.
55. Q55: Write the reaction for the preparation of calcium oxide from calcium carbonate.
    A: CaCO₃ → CaO + CO₂ (on heating).
56. Q56: What happens when sodium hydroxide is added to aqueous sodium chloride?
    A: No reaction; the solution remains neutral.
Part 3: Halides, Hydroxides, and Carbonates
57. Q57: What type of oxides do alkali metals form?
    A: Alkali metals form peroxides (e.g., Na₂O₂), superoxides (e.g., KO₂), and normal oxides (Li₂O).
58. Q58: Which alkali metal forms superoxides and why?
    A: Potassium, rubidium, and cesium form superoxides due to their larger size and ability to stabilize the large superoxide ion.
59. Q59: What are the common oxides of alkaline earth metals?
    A: Oxides such as BeO, MgO, CaO, SrO, BaO.
60. Q60: What type of hydroxides do alkali metals form?
    A: Strong alkaline hydroxides, e.g., NaOH, KOH.
61. Q61: What is the trend in solubility of alkaline earth metal hydroxides?
    A: Solubility increases down the group from Be to Ba.
62. Q62: Which alkaline earth metal hydroxide is least soluble in water?
    A: Beryllium hydroxide is least soluble in water.
63. Q63: What type of halides do alkali metals form?
    A: Ionic halides with high melting points.
64. Q64: Describe the thermal stability trend of alkaline earth metal carbonates.
    A: Thermal stability increases down the group.
65. Q65: Give a characteristic property of alkali metal halides.
    A: High melting and boiling points due to strong ionic bonds.
66. Q66: Describe the solubility trend of alkaline earth metal sulfates.
    A: Solubility decreases down the group.
67. Q67: What type of oxides does calcium form?
    A: Calcium forms basic oxides such as calcium oxide (CaO).
68. Q68: Explain the solubility of alkali metal salts in water.
    A: Alkali metal salts are generally highly soluble in water due to ionic bonding.
69. Q69: Discuss the thermal stability of alkaline earth metal nitrates.
    A: Stability increases down the group; lighter ones decompose to oxides and nitrogen dioxide, heavier ones form nitrites.
70. Q70: What is the nature of bonding in alkaline earth metal halides?
    A: Mostly ionic, but Be halides have covalent character.
71. Q71: Why does beryllium chloride have a low melting point compared to other group 2 halides?
    A: Due to its covalent molecular structure.
72. Q72: Describe the solubility of calcium sulfate in water.
    A: Moderately soluble with low solubility compared to other calcium salts.
73. Q73: What is the nature of oxides formed by alkaline earth metals?
    A: Basic oxides.
74. Q74: How does the solubility of alkali metal hydroxides change down the group?
    A: Solubility increases from LiOH to CsOH.
75. Q75: State a common property of Group 1 and Group 2 metal oxides.
    A: Most are basic in nature.
76. Q76: What is the nature of bonding in sodium hydroxide?
    A: Ionic bonding with polar covalent nature in metal hydroxides.
Part 4: Anomalous Behavior and Diagonal Relationships
77. Q77: Why is lithium different from other alkali metals?
    A: Lithium shows anomalous behavior due to its small size, high ionization enthalpy, and high polarizing power.
78. Q78: Why is beryllium different from other alkaline earth metals?
    A: Due to its small size, high ionization enthalpy, and covalent bonding characteristics.
79. Q79: Which alkali metal exhibits diagonal relationship with magnesium?
    A: Lithium exhibits diagonal relationship with magnesium.
80. Q80: Why is lithium carbonate insoluble in water?
    A: Due to the high lattice enthalpy and covalent character of lithium carbonate.
81. Q81: What is the nature of bonding in beryllium chloride?
    A: Covalent bonding due to small size and high polarizing power of Be²⁺.
82. Q82: Why does lithium form more covalent compounds compared to other alkali metals?
    A: Due to its small size and high polarizing power.
83. Q83: What is "diagonal relationship" in the context of s-block elements?
    A: Similarity in properties of diagonally adjacent elements in the periodic table, e.g., Li and Mg.
84. Q84: What is the anomalous behavior of beryllium in the group 2 elements?
    A: Beryllium shows high ionization energy, small size, and more covalent character in its compounds compared to other group 2 elements.
85. Q85: Why is beryllium hydroxide amphoteric?
    A: Because it can react with both acids and bases forming salts and complexes respectively.
86. Q86: What is the diagonal relationship between beryllium and aluminum?
    A: Similarities in chemical behavior due to similar charge density and covalent character.
87. Q87: Why does lithium form covalent compounds despite being a metal?
    A: Due to its small ionic size and high polarizing power.
88. Q88: Why does beryllium have a higher melting point compared to other group 2 metals?
    A: Due to strong covalent bonding and small atomic size.
89. Q89: Define the diagonal relationship with an example.
    A: Similarity in properties of two elements diagonally positioned in the periodic table like Li and Mg.
90. Q90: Why does beryllium have a higher ionization energy compared to magnesium?
    A: Because of smaller size and stronger attraction for electrons.
91. Q91: Why is beryllium chloride covalent while other group 2 chlorides are ionic?
    A: Due to the small size and high polarizing power of Be²⁺ ion.
92. Q92: Which alkali metal exhibits the greatest tendency to form organometallic compounds?
    A: Lithium.
Part 5: Uses and Specific Compounds
93. Q93: What are the common uses of sodium?
    A: Sodium is used in the synthesis of organic compounds, sodium vapor lamps, and as a reducing agent.
94. Q94: Give the uses of calcium hydroxide.
    A: Used in construction (plaster), water treatment, and as a neutralizing agent.
95. Q95: What is the role of calcium oxide in the steel industry?
    A: Used as a flux to remove impurities.
96. Q96: What is the use of sodium bicarbonate?
    A: Used as an antacid, in baking, and for fire extinguishers.
97. Q97: Why is calcium used in the extraction of metals?
    A: It is a strong reducing agent and can reduce metal oxides.
98. Q98: Which alkali metal is used in photoelectric cells?
    A: Cesium.
99. Q99: Why is magnesium used in the synthesis of Grignard reagents?
    A: Its moderate reactivity and ability to form organomagnesium compounds make it suitable.
100. Q100: What is the use of lime (CaO)?
     A: Used in cement, steel making, and to neutralize acidic soils.
101. Q101: Give the commercial use of sodium hydroxide.
     A: Used in the manufacture of soap, paper, and detergents.
102. Q102: How is calcium carbonate naturally found?
     A: As limestone, chalk, and marble.
103. Q103: What is the role of sodium hydroxide in the Bayer process?
     A: It is used to extract alumina from bauxite ore.
104. Q104: What is the application of calcium sulfate?
     A: Used in plaster of Paris and as a building material.
105. Q105: How is sodium metal prepared commercially?
     A: By the electrolysis of molten sodium chloride.
106. Q106: Mention the use of sodium bicarbonate in medicine.
     A: Used as an antacid to relieve acidity.
107. Q107: Write the uses of sodium chloride.
     A: Used as common salt in food, in chemical industries, and for de-icing.
108. Q108: Give a reason why calcium is used in the extraction of uranium and thorium.
     A: It acts as a strong reducing agent for these metals.
109. Q109: Why is calcium hydroxide called slaked lime?
     A: Because it is produced by adding water to quicklime (CaO).
110. Q110: Mention one use of sodium peroxide.
     A: Used as a bleaching agent and oxygen source.

s-Block Elements Quiz (30 MCQs)

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