Periodic Classification of Elements Part 2: MCQs (Q26–Q50)
📘 Periodic Classification of Elements – MCQs
🔹 Part 2: Questions 26–50
Q26. The element with electronic configuration 2,8,7 belongs to:
A) Group 1, Period 2
B) Group 17, Period 3
C) Group 16, Period 3
D) Group 18, Period 2
Correct Answer: B) Group 17, Period 3
Explanation:
- A) Group 1, Period 2 → Group 1 has ns¹ configuration. Wrong.
- ✅ B) Group 17, Period 3 → 2,8,7 → 7 valence electrons → Halogen (Cl).
- C) Group 16, Period 3 → Group 16 has 6 valence electrons.
- D) Group 18, Period 2 → Noble gases have ns²np⁶.
Q27. Which of the following is a transition element?
A) Sodium
B) Calcium
C) Iron
D) Potassium
Correct Answer: C) Iron
Explanation:
- A) Sodium → Alkali metal.
- B) Calcium → Alkaline earth metal.
- ✅ C) Iron → Transition element (d-block).
- D) Potassium → Alkali metal.
Q28. An element with atomic number 12 will be placed in:
A) Group 2, Period 3
B) Group 12, Period 2
C) Group 2, Period 2
D) Group 3, Period 2
Correct Answer: A) Group 2, Period 3
Explanation:
- Atomic number 12 = Mg = 2,8,2.
- ✅ A) Group 2 (2 valence e⁻), Period 3 (3 shells).
- B, C, D → Wrong placements.
Q29. The outermost shell of noble gases is completely filled with:
A) 6 electrons
B) 7 electrons
C) 8 electrons
D) 2 electrons
Correct Answer: C) 8 electrons
Explanation:
- A) 6 → Group 16 elements.
- B) 7 → Halogens.
- ✅ C) 8 → Noble gases (except He = 2).
- D) 2 → Only helium.
Q30. The most electropositive element is:
A) Sodium
B) Cesium
C) Lithium
D) Potassium
Correct Answer: B) Cesium
Explanation:
- A) Sodium → Reactive, but not most.
- ✅ B) Cesium → At the bottom of Group 1, maximum tendency to lose electron.
- C) Lithium → Least electropositive in group 1.
- D) Potassium → Less electropositive than Cs.
Q31. Which of the following does not belong to the halogen family?
A) Fluorine
B) Bromine
C) Chlorine
D) Oxygen
Correct Answer: D) Oxygen
Explanation:
- A, B, C → Group 17 halogens.
- ✅ D) Oxygen → Group 16, chalcogen.
Q32. Which of the following is the lightest alkali metal?
A) Sodium
B) Potassium
C) Lithium
D) Cesium
Correct Answer: C) Lithium
Explanation:
- A) Sodium, B) Potassium, D) Cesium → Heavier than lithium.
- ✅ C) Lithium → Atomic number 3, lightest alkali metal.
Q33. Which of the following pairs are chemically similar?
A) Na and Mg
B) Na and K
C) Na and Cl
D) Na and Al
Correct Answer: B) Na and K
Explanation:
- A) Na & Mg → Different groups.
- ✅ B) Na & K → Same group 1, similar properties.
- C) Na & Cl → Metal and non-metal, not similar.
- D) Na & Al → Different groups.
Q34. Which element has the smallest atomic size in Period 2?
A) Lithium
B) Oxygen
C) Fluorine
D) Neon
Correct Answer: D) Neon
Explanation:
- A) Lithium → Largest in period 2.
- B) Oxygen, C) Fluorine → Smaller but not the smallest.
- ✅ D) Neon → Noble gas, smallest due to maximum nuclear pull.
Q35. Which of the following will form an acidic oxide?
A) Na₂O
B) MgO
C) Al₂O₃
D) SO₂
Correct Answer: D) SO₂
Explanation:
- A) Na₂O → Strongly basic oxide.
- B) MgO → Basic oxide.
- C) Al₂O₃ → Amphoteric oxide.
- ✅ D) SO₂ → Acidic oxide (non-metal oxide).
Q36. Which of the following is NOT a periodic property?
A) Atomic size
B) Ionization energy
C) Valency
D) Mass number
Correct Answer: D) Mass number
Explanation:
- A, B, C → Periodic properties.
- ✅ D) Mass number → Not periodic, depends on isotope.
Q37. Which of the following elements has 2 valence electrons?
A) Na
B) Mg
C) Al
D) Cl
Correct Answer: B) Mg
Explanation:
- A) Na → 1 valence electron.
- ✅ B) Mg → 2 valence electrons (2,8,2).
- C) Al → 3 valence electrons.
- D) Cl → 7 valence electrons.
Q38. The first element of each period is always a:
A) Noble gas
B) Non-metal
C) Alkali metal
D) Halogen
Correct Answer: C) Alkali metal
Explanation:
- A) Noble gas → Last element of period.
- B) Non-metal → Not first.
- ✅ C) Alkali metal → 1 valence electron, starts each period.
- D) Halogen → Second-last of period.
Q39. Which of the following will have highest ionization energy?
A) Na
B) K
C) Rb
D) Li
Correct Answer: D) Li
Explanation:
- A) Na, B) K, C) Rb → Larger atoms, lower IE.
- ✅ D) Li → Smallest atom in group 1, highest IE.
Q40. Which of the following will have lowest electronegativity?
A) Fluorine
B) Oxygen
C) Cesium
D) Chlorine
Correct Answer: C) Cesium
Explanation:
- A) Fluorine → Highest EN.
- B) Oxygen, D) Chlorine → High EN.
- ✅ C) Cesium → Lowest EN, strong metallic nature.
Q41. Which of the following is an amphoteric oxide?
A) Na₂O
B) MgO
C) Al₂O₃
D) SO₂
Correct Answer: C) Al₂O₃
Explanation:
- A) Na₂O → Basic oxide.
- B) MgO → Basic oxide.
- ✅ C) Al₂O₃ → Amphoteric, reacts with both acids & bases.
- D) SO₂ → Acidic oxide.
Q42. The element with atomic number 17 is:
A) Oxygen
B) Chlorine
C) Sodium
D) Sulphur
Correct Answer: B) Chlorine
Explanation:
- Atomic number 17 = Cl.
- ✅ B) Chlorine → Group 17 halogen.
- Others → Wrong atomic numbers.
Q43. Which of the following belongs to the p-block?
A) Fe
B) Ca
C) Cl
D) Na
Correct Answer: C) Cl
Explanation:
- A) Fe → d-block.
- B) Ca → s-block.
- ✅ C) Cl → p-block element.
- D) Na → s-block.
Q44. Which of the following is a metalloid?
A) Sodium
B) Boron
C) Magnesium
D) Chlorine
Correct Answer: B) Boron
Explanation:
- A) Sodium → Metal.
- ✅ B) Boron → Metalloid.
- C) Magnesium → Metal.
- D) Chlorine → Non-metal.
Q45. Which of the following elements has the largest atomic radius?
A) Na
B) K
C) Rb
D) Cs
Correct Answer: D) Cs
Explanation:
- ✅ D) Cs → Atomic radius increases down group, Cs is largest.
- A, B, C → Smaller radii.
Q46. Which of the following elements has the lowest atomic radius in Period 3?
A) Na
B) Mg
C) Cl
D) Ar
Correct Answer: D) Ar
Explanation:
- Across a period, atomic radius decreases.
- ✅ D) Ar → Last element in period, smallest radius.
Q47. Which of the following is NOT a representative element?
A) Na
B) Cl
C) Fe
D) Mg
Correct Answer: C) Fe
Explanation:
- ✅ C) Fe → Transition element (d-block), not representative.
- A, B, D → s- and p-block, representative elements.
Q48. Which element has the electronic configuration 2,8,2?
A) Sodium
B) Magnesium
C) Aluminum
D) Calcium
Correct Answer: B) Magnesium
Explanation:
- ✅ B) Mg → 12 = 2,8,2.
- A) Na → 2,8,1.
- C) Al → 2,8,3.
- D) Ca → 2,8,8,2.
Q49. Which of the following elements belongs to Group 16?
A) Nitrogen
B) Oxygen
C) Fluorine
D) Neon
Correct Answer: B) Oxygen
Explanation:
- A) Nitrogen → Group 15.
- ✅ B) Oxygen → Group 16 (chalcogen).
- C) Fluorine → Group 17.
- D) Neon → Group 18.
Q50. Which group of elements shows maximum similarity in chemical properties?
A) Elements in same period
B) Elements in same group
C) Transition elements
D) Lanthanides
Correct Answer: B) Elements in same group
Explanation:
- A) Same period → Different valence electrons.
- ✅ B) Same group → Same valence electrons, maximum similarity.
- C, D → Show similarity, but not as consistent as groups.
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