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Periodic Classification of Elements CBSE Class 10 MCQ & Practice Questions

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Periodic Classification of Elements Revision Guide for CBSE Class 10 Chemistry

Periodic Classification of Elements is part of CBSE Class 10 Chemistry preparation. A strong revision plan should combine concept review with exam-style questions so that definitions, relationships, calculations and exceptions are recalled accurately.

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Top 20 Periodic Classification of Elements MCQs with Answers

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CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

1. The modern periodic law is based on periodicity of properties with respect to:

  • A. Atomic mass
  • B. Mass number
  • C. Atomic number
  • D. Number of neutrons
Answer: C
Explanation: Modern periodic law states that properties are periodic functions of atomic number.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

2. Mendeleev arranged elements mainly in increasing order of:

  • A. Atomic number
  • B. Atomic mass
  • C. Density
  • D. Valency only
Answer: B
Explanation: Mendeleev's periodic table was based primarily on increasing atomic mass.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

3. An element with electronic configuration 2,8,1 belongs to:

  • A. Group 17
  • B. Group 18
  • C. Group 1
  • D. Group 2
Answer: C
Explanation: It has one valence electron, so it belongs to Group 1.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

4. An element with electronic configuration 2,8,7 belongs to:

  • A. Group 1
  • B. Group 2
  • C. Group 17
  • D. Group 18
Answer: C
Explanation: Seven valence electrons place the element in Group 17.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

5. The period number of an element equals the number of:

  • A. Valence electrons
  • B. Neutrons
  • C. Occupied electron shells
  • D. Protons plus neutrons
Answer: C
Explanation: The number of occupied shells determines the period.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

6. Across a period from left to right, atomic size generally:

  • A. Increases
  • B. Remains constant
  • C. Decreases
  • D. First decreases then always doubles
Answer: C
Explanation: Effective nuclear charge increases while electrons enter the same shell, pulling them closer.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

7. Down a group, atomic size generally:

  • A. Decreases
  • B. Remains fixed
  • C. Increases
  • D. Becomes zero
Answer: C
Explanation: A new electron shell is added at each successive period down a group.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

8. Across a period, metallic character generally:

  • A. Increases
  • B. Remains unchanged
  • C. Decreases
  • D. Becomes maximum at noble gases
Answer: C
Explanation: The tendency to lose electrons decreases from left to right.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

9. Down a group, metallic character generally:

  • A. Decreases
  • B. Remains unchanged
  • C. Increases
  • D. Disappears
Answer: C
Explanation: Larger atoms lose valence electrons more easily down a group.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

10. Which element is the most electronegative?

  • A. Oxygen
  • B. Chlorine
  • C. Fluorine
  • D. Nitrogen
Answer: C
Explanation: Fluorine has the highest electronegativity.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

11. Which order correctly represents increasing atomic size in Period 3?

  • A. Na < Mg < Al < Si
  • B. Cl < S < P < Si < Al < Mg < Na
  • C. Na < Cl < Mg < S
  • D. Si < P < Al < Na < Cl
Answer: B
Explanation: Atomic size decreases across Period 3, so the increasing order is Cl < S < P < Si < Al < Mg < Na.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

12. Which order correctly represents increasing metallic character in Period 3?

  • A. Na < Mg < Al < Si < P < S < Cl
  • B. Cl < S < P < Si < Al < Mg < Na
  • C. Cl < Na < Mg < Al
  • D. Si < Cl < Na < Mg
Answer: B
Explanation: Metallic character decreases across a period, so the increasing order is from Cl toward Na.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

13. Valency across a main-group period generally changes as:

  • A. 1,2,3,4,5,6,7,8
  • B. 0,1,2,3,4,5,6,7
  • C. 1,2,3,4,3,2,1,0
  • D. 8,7,6,5,4,3,2,1
Answer: C
Explanation: Valency increases from 1 to 4 and then decreases to 0.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

14. Which oxide is amphoteric?

  • A. Na₂O
  • B. SO₃
  • C. Al₂O₃
  • D. Cl₂O₇
Answer: C
Explanation: Aluminium oxide reacts with both acids and bases.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

15. Which oxide is strongly basic?

  • A. SO₂
  • B. CO₂
  • C. Na₂O
  • D. SiO₂
Answer: C
Explanation: Na₂O is an ionic oxide of a highly electropositive metal.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

16. Across a period, the acidic character of oxides generally:

  • A. Decreases
  • B. Remains constant
  • C. Increases
  • D. Becomes random
Answer: C
Explanation: Non-metallic character increases across a period, making oxides more acidic.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

17. Why do isotopes occupy the same position in the modern periodic table?

  • A. They have the same atomic mass
  • B. They have the same mass number
  • C. They have the same atomic number
  • D. They have the same neutron number
Answer: C
Explanation: Periodic position is determined by atomic number, which is identical for isotopes.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

18. Noble gases are chemically inert mainly because they have:

  • A. One valence electron
  • B. Two incomplete shells
  • C. Completely filled valence shells
  • D. No nucleus
Answer: C
Explanation: A complete valence shell is highly stable.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

19. Halogens generally form −1 ions because they:

  • A. Have one valence electron
  • B. Need one electron to complete the octet
  • C. Lose seven electrons easily
  • D. Have zero valency in all compounds
Answer: B
Explanation: Halogens have seven valence electrons and tend to gain one.

CBSE Class 10 Chemistry · Periodic Classification of Elements · Very Very Hard

20. Alkali metals are highly reactive because they:

  • A. Have seven valence electrons
  • B. Have a complete octet
  • C. Lose one valence electron easily
  • D. Cannot form ions
Answer: C
Explanation: Their single valence electron is lost readily due to low ionisation energy.

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