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Classification of Elements and Periodicity in Properties CBSE Class 11 MCQ & Practice Questions

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Classification of Elements and Periodicity in Properties Revision Guide for CBSE Class 11 Chemistry

Classification of Elements and Periodicity in Properties is part of CBSE Class 11 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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Important Topics

  • Core definitions and principles
  • Important equations or relationships
  • Common applications and examples
  • Frequently confused concepts
  • Exam-style multiple-choice questions
  • Error review and targeted revision

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Top 20 Classification of Elements and Periodicity in Properties MCQs with Answers

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CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

1. The modern periodic law states that elemental properties are periodic functions of:

  • A. Atomic mass
  • B. Atomic number
  • C. Mass number
  • D. Number of neutrons
Answer: B
Explanation: Modern periodicity is based on atomic number and therefore on electronic configuration.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

2. The long form periodic table contains:

  • A. 7 periods and 18 groups
  • B. 8 periods and 16 groups
  • C. 6 periods and 18 groups
  • D. 7 periods and 8 groups
Answer: A
Explanation: The modern periodic table contains seven periods and eighteen groups.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

3. An element with valence-shell configuration 3s²3p⁵ belongs to:

  • A. Period 3, Group 15
  • B. Period 3, Group 17
  • C. Period 5, Group 3
  • D. Period 2, Group 17
Answer: B
Explanation: The highest principal quantum number is 3, and ns²np⁵ corresponds to Group 17.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

4. An element with configuration

  • A. Period 2, Group 2
  • B. Period 3, Group 2
  • C. Period 3, Group 12
  • D. Period 2, Group 12
Answer: B
Explanation: The highest n value is 3 and two s-electrons place it in Group 2.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

5. The general valence-shell configuration of p-block elements is:

  • A. ns¹–²
  • B. (n−1)d¹–¹⁰ns⁰–²
  • C. ns²np¹–⁶
  • D. (n−2)f¹–¹⁴(n−1)d⁰–¹ns²
Answer: C
Explanation: p-block elements have valence configuration ns²np¹–⁶.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

6. Which element belongs to the d-block?

  • A. Na
  • B. Cl
  • C. Fe
  • D. Ce
Answer: C
Explanation: Iron has partially filled d-orbitals and is a d-block element.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

7. Which pair shows a diagonal relationship?

  • A. Li and Mg
  • B. Na and Mg
  • C. Be and Mg
  • D. B and Al
Answer: A
Explanation: Lithium and magnesium show diagonal similarity due to comparable charge density.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

8. Across a period, effective nuclear charge generally:

  • A. Decreases
  • B. Increases
  • C. Remains constant
  • D. Becomes zero
Answer: B
Explanation: Nuclear charge increases while shielding changes relatively little within the same shell.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

9. Across a period, atomic radius generally:

  • A. Increases
  • B. Decreases
  • C. Remains constant
  • D. First doubles and then falls
Answer: B
Explanation: Increasing effective nuclear charge pulls electrons closer to the nucleus.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

10. Down a group, atomic radius generally increases because:

  • A. Effective nuclear charge becomes zero
  • B. New electron shells are added
  • C. Nuclear charge decreases
  • D. Valence electrons enter the same shell
Answer: B
Explanation: Successive elements contain an additional principal shell.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

11. Which has the smallest atomic radius?

  • A. Na
  • B. Mg
  • C. Al
  • D. Cl
Answer: D
Explanation: Atomic radius decreases across Period 3, making chlorine the smallest among these.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

12. Which species has the largest radius in the isoelectronic series O²⁻, F⁻, Na⁺, Mg²⁺?

  • A. O²⁻
  • B. F⁻
  • C. Na⁺
  • D. Mg²⁺
Answer: A
Explanation: All have ten electrons; O²⁻ has the lowest nuclear charge and therefore the largest radius.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

13. A cation is smaller than its parent atom mainly because:

  • A. It gains electrons
  • B. Electron loss reduces repulsion and may remove the outer shell
  • C. Its nuclear charge decreases
  • D. Its proton number decreases
Answer: B
Explanation: Electron loss increases attraction per remaining electron and can remove the valence shell.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

14. An anion is larger than its parent atom mainly because:

  • A. It loses a shell
  • B. Added electrons increase electron-electron repulsion
  • C. Its nuclear charge increases
  • D. Its proton number increases
Answer: B
Explanation: Adding electrons increases repulsion within the same shell and expands the electron cloud.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

15. First ionisation enthalpy generally increases across a period because:

  • A. Atomic size increases
  • B. Effective nuclear charge increases
  • C. Shielding increases sharply
  • D. Valence electrons enter a new shell
Answer: B
Explanation: Smaller size and greater effective nuclear charge hold the outer electron more strongly.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

16. Which has the lowest first ionisation enthalpy?

  • A. Li
  • B. Na
  • C. K
  • D. Rb
Answer: D
Explanation: Ionisation enthalpy decreases down Group 1; rubidium is lowest among the choices.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

17. The first ionisation enthalpy of Be is greater than that of B because:

  • A. Be is larger
  • B. Be has a completely filled 2s subshell
  • C. B has no p-electron
  • D. Be has lower nuclear charge
Answer: B
Explanation: Removing an electron from the stable filled 2s² subshell of Be requires more energy than removing B's 2p electron.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

18. The first ionisation enthalpy of N is greater than that of O because:

  • A. N has a half-filled 2p³ configuration
  • B. O has lower nuclear charge
  • C. N has larger radius
  • D. O has no paired electrons
Answer: A
Explanation: The half-filled 2p³ configuration of nitrogen is especially stable; paired-electron repulsion lowers oxygen's value.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

19. Electron gain enthalpy is most negative for:

  • A. F
  • B. Cl
  • C. Br
  • D. I
Answer: B
Explanation: Chlorine has a more negative electron gain enthalpy than fluorine because its larger 3p shell has less electron-electron repulsion.

CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Very Very Hard

20. Why is the electron gain enthalpy of noble gases positive?

  • A. They have low nuclear charge
  • B. The added electron must enter a higher-energy shell
  • C. They are highly metallic
  • D. They have one valence electron
Answer: B
Explanation: Noble gases possess closed shells; an extra electron enters the next higher shell and requires energy.

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