Periodic Classification of Elements Part 3: MCQs (Q51–Q75)
📘 Periodic Classification of Elements – MCQs
🔹 Part 3: Questions 51–75
Q51. Which of the following statements is true about noble gases?
A) They are highly reactive.
B) They have completely filled valence shells.
C) They belong to Group 17.
D) They form many compounds.
Correct Answer: B) They have completely filled valence shells
Explanation:
- A) Highly reactive → Wrong; they are chemically inert.
- ✅ B) Completely filled valence shell (ns²np⁶ or 2 for He).
- C) Group 17 → Incorrect; noble gases are Group 18.
- D) Many compounds → Wrong; they form very few.
Q52. Which element is placed in Group 1, Period 4?
A) Potassium
B) Sodium
C) Calcium
D) Magnesium
Correct Answer: A) Potassium
Explanation:
- ✅ A) Potassium (K, Z=19 → 2,8,8,1).
- B) Sodium → Period 3, Group 1.
- C) Calcium → Group 2, Period 4.
- D) Magnesium → Group 2, Period 3.
Q53. Which of the following increases as we move from left to right across a period?
A) Atomic size
B) Metallic character
C) Ionization energy
D) Electropositivity
Correct Answer: C) Ionization energy
Explanation:
- A) Atomic size → Decreases.
- B) Metallic character → Decreases.
- ✅ C) Ionization energy → Increases (harder to remove e⁻).
- D) Electropositivity → Decreases.
Q54. Which of the following decreases down a group?
A) Atomic size
B) Ionization energy
C) Metallic character
D) Atomic number
Correct Answer: B) Ionization energy
Explanation:
- A) Atomic size → Increases down a group.
- ✅ B) Ionization energy → Decreases due to increased distance from nucleus.
- C) Metallic character → Increases.
- D) Atomic number → Always increases.
Q55. The outermost electronic configuration of halogens is:
A) ns¹
B) ns²np⁵
C) ns²np⁶
D) ns²np⁴
Correct Answer: B) ns²np⁵
Explanation:
- A) ns¹ → Alkali metals.
- ✅ B) ns²np⁵ → Halogens, 7 valence electrons.
- C) ns²np⁶ → Noble gases.
- D) ns²np⁴ → Group 16 (O, S).
Q56. Which of the following is an alkaline earth metal?
A) Sodium
B) Calcium
C) Potassium
D) Iron
Correct Answer: B) Calcium
Explanation:
- A) Sodium → Group 1.
- ✅ B) Calcium → Group 2 (alkaline earth metal).
- C) Potassium → Group 1.
- D) Iron → Transition metal.
Q57. The number of valence electrons in Group 13 elements is:
A) 1
B) 2
C) 3
D) 5
Correct Answer: C) 3
Explanation:
- A) 1 → Group 1.
- B) 2 → Group 2.
- ✅ C) 3 → Group 13 (B, Al, Ga).
- D) 5 → Group 15.
Q58. Which of the following has the highest electronegativity?
A) Oxygen
B) Fluorine
C) Chlorine
D) Sulphur
Correct Answer: B) Fluorine
Explanation:
- A) Oxygen → High but not highest.
- ✅ B) Fluorine → Highest electronegativity in the periodic table.
- C) Chlorine, D) Sulphur → Lower EN.
Q59. Which of the following elements is placed in Group 18?
A) Argon
B) Fluorine
C) Sulphur
D) Phosphorus
Correct Answer: A) Argon
Explanation:
- ✅ A) Argon → Noble gas, Group 18.
- B) Fluorine → Group 17.
- C) Sulphur → Group 16.
- D) Phosphorus → Group 15.
Q60. Which of the following is a characteristic property of non-metals?
A) They are malleable
B) They are ductile
C) They are good conductors of heat
D) They form acidic oxides
Correct Answer: D) They form acidic oxides
Explanation:
- A, B, C → Metallic properties.
- ✅ D) Non-metals form acidic oxides (e.g., SO₂, CO₂).
Q61. Which element among the following belongs to Period 2 and Group 1?
A) Lithium
B) Sodium
C) Potassium
D) Magnesium
Correct Answer: A) Lithium
Explanation:
- ✅ A) Lithium → Period 2, Group 1.
- B) Sodium → Period 3, Group 1.
- C) Potassium → Period 4, Group 1.
- D) Magnesium → Group 2, Period 3.
Q62. The elements in the same group have similar chemical properties because they have:
A) Same atomic size
B) Same number of shells
C) Same number of valence electrons
D) Same atomic mass
Correct Answer: C) Same number of valence electrons
Explanation:
- A) Atomic size → Different.
- B) Shells → Different in periods.
- ✅ C) Valence electrons → Governs chemical properties.
- D) Mass → Varies.
Q63. Which of the following is the least reactive halogen?
A) Fluorine
B) Chlorine
C) Bromine
D) Iodine
Correct Answer: D) Iodine
Explanation:
- Reactivity decreases down Group 17.
- ✅ D) Iodine → Least reactive halogen.
Q64. Which of the following is the heaviest noble gas?
A) Xenon
B) Argon
C) Neon
D) Radon
Correct Answer: D) Radon
Explanation:
- ✅ D) Radon → Last noble gas, heaviest.
- Others → Lighter noble gases.
Q65. Which of the following trends is correct across a period?
A) Atomic size increases
B) Metallic character increases
C) Non-metallic character increases
D) Ionization energy decreases
Correct Answer: C) Non-metallic character increases
Explanation:
- A) Atomic size decreases.
- B) Metallic character decreases.
- ✅ C) Non-metallic character increases.
- D) Ionization energy increases.
Q66. Which of the following trends is correct down a group?
A) Atomic size decreases
B) Electronegativity increases
C) Metallic character increases
D) Ionization energy increases
Correct Answer: C) Metallic character increases
Explanation:
- A) Size → Increases.
- B) EN → Decreases.
- ✅ C) Metallic character → Increases.
- D) IE → Decreases.
Q67. Which of the following pairs is NOT correctly matched?
A) Group 1 – Alkali metals
B) Group 2 – Alkaline earth metals
C) Group 17 – Noble gases
D) Group 18 – Inert gases
Correct Answer: C) Group 17 – Noble gases
Explanation:
- ✅ C) Group 17 → Halogens, not noble gases.
- Others → Correctly matched.
Q68. Which of the following is an inner transition element?
A) Iron
B) Uranium
C) Sodium
D) Calcium
Correct Answer: B) Uranium
Explanation:
- A) Fe → Transition element.
- ✅ B) Uranium → Actinide, inner transition element.
- C, D → Main group elements.
Q69. Which of the following elements will form basic oxides?
A) Sulphur
B) Carbon
C) Sodium
D) Chlorine
Correct Answer: C) Sodium
Explanation:
- A) Sulphur, B) Carbon, D) Chlorine → Non-metals → Acidic oxides.
- ✅ C) Sodium → Metal → Forms basic oxide (Na₂O).
Q70. Which of the following will show variable valency?
A) Na
B) Mg
C) Fe
D) Cl
Correct Answer: C) Fe
Explanation:
- A) Na → Fixed +1.
- B) Mg → Fixed +2.
- ✅ C) Fe → +2, +3 (variable valency).
- D) Cl → Can vary, but Fe is the standard example in NCERT.
Q71. Which of the following is the lightest noble gas?
A) Helium
B) Neon
C) Argon
D) Krypton
Correct Answer: A) Helium
Explanation:
- ✅ A) Helium → Atomic number 2, lightest noble gas.
- Others → Heavier noble gases.
Q72. Which of the following elements has the maximum tendency to gain electrons?
A) Sodium
B) Fluorine
C) Magnesium
D) Neon
Correct Answer: B) Fluorine
Explanation:
- A) Na → Tends to lose electrons.
- ✅ B) Fluorine → Highest electron affinity.
- C) Mg → Loses electrons.
- D) Neon → Stable, does not gain e⁻.
Q73. Which of the following belongs to the d-block?
A) Na
B) Mg
C) Fe
D) Al
Correct Answer: C) Fe
Explanation:
- A) Na, B) Mg, D) Al → s/p block.
- ✅ C) Fe → Transition metal, d-block.
Q74. Which element among the following is placed in Period 2, Group 17?
A) Fluorine
B) Chlorine
C) Bromine
D) Iodine
Correct Answer: A) Fluorine
Explanation:
- ✅ A) Fluorine → Period 2, Group 17.
- B, C, D → Same group, but lower periods.
Q75. Which of the following is a property of metals?
A) Form acidic oxides
B) Gain electrons
C) Good conductors of heat and electricity
D) Brittle in nature
Correct Answer: C) Good conductors of heat and electricity
Explanation:
- A) Acidic oxides → Non-metals.
- B) Gain electrons → Non-metals.
- ✅ C) Metals → Conduct heat & electricity.
- D) Brittle → Non-metals.
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