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

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

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

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

1. According to the Modern Periodic Law, the properties of elements are periodic functions of their:

  • A. Neutron numbers
  • B. Mass numbers
  • C. Atomic numbers
  • D. Atomic masses
Answer: C
Explanation: Modern periodic law uses atomic number as the fundamental basis of classification.

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

2. Mendeleev arranged elements primarily in order of increasing:

  • A. Ionisation enthalpy
  • B. Atomic mass
  • C. Atomic number
  • D. Density
Answer: B
Explanation: Mendeleev's original periodic classification was based mainly on atomic masses and recurring properties.

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

3. The modern periodic table contains:

  • A. 18 groups
  • B. 8 groups
  • C. 16 groups
  • D. 7 groups
Answer: A
Explanation: The long-form periodic table has 18 vertical groups.

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

4. Elements of Group 1 have general outer electronic configuration:

  • A. ns2np1
  • B. ns2np5
  • C. ns1
  • D. ns2
Answer: C
Explanation: Alkali metals have one valence electron in an s orbital.

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

5. Elements of Group 2 generally have outer configuration:

  • A. ns2np6
  • B. ns2
  • C. ns1
  • D. ns2np2
Answer: B
Explanation: Alkaline-earth metals possess two outer s electrons.

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

6. The p-block generally includes Groups:

  • A. 13 to 18
  • B. 1 and 2
  • C. 3 to 12
  • D. Only 18
Answer: A
Explanation: The differentiating electron of p-block elements enters a p subshell.

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

7. The d-block elements occupy Groups:

  • A. 1 to 2
  • B. 13 to 18
  • C. Only 17 and 18
  • D. 3 to 12
Answer: D
Explanation: Transition elements occupy the central ten groups of the long-form table.

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

8. The f-block elements are commonly called:

  • A. Alkali metals
  • B. Halogens
  • C. Inner transition elements
  • D. Noble gases
Answer: C
Explanation: Lanthanides and actinides involve filling of inner f orbitals.

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

9. Across a period from left to right, atomic radius generally:

  • A. First becomes infinite
  • B. Decreases
  • C. Increases
  • D. Remains exactly constant
Answer: B
Explanation: Effective nuclear charge increases while electrons enter the same principal shell.

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

10. Down a group, atomic radius generally:

  • A. Increases
  • B. Decreases
  • C. Remains constant
  • D. Becomes zero
Answer: A
Explanation: Successive members possess additional electron shells.

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

11. A cation is generally:

  • A. Larger than its parent atom
  • B. Exactly equal in radius
  • C. Always neutral
  • D. Smaller than its parent atom
Answer: D
Explanation: Electron loss reduces electron-electron repulsion and often removes the outer shell.

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

12. An anion is generally:

  • A. Identical in radius
  • B. Without electrons
  • C. Larger than its parent atom
  • D. Smaller than its parent atom
Answer: C
Explanation: Electron gain increases repulsion among electrons, expanding the electron cloud.

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

13. In an isoelectronic series, radius generally decreases with increasing:

  • A. Negative charge
  • B. Nuclear charge
  • C. Number of shells
  • D. Electron count
Answer: B
Explanation: For the same number of electrons, greater nuclear charge attracts the electron cloud more strongly.

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

14. Among O2-, F-, Na+ and Mg2+, the smallest species is:

  • A. Mg2+
  • B. O2-
  • C. F-
  • D. Na+
Answer: A
Explanation: All are isoelectronic with 10 electrons; Mg2+ has the greatest nuclear charge.

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

15. Among O2-, F-, Na+ and Mg2+, the largest species is:

  • A. Mg2+
  • B. Na+
  • C. F-
  • D. O2-
Answer: D
Explanation: All have 10 electrons; O2- has the smallest nuclear charge and hence the largest radius.

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

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

  • A. Shielding becomes infinitely large
  • B. Nuclear charge decreases
  • C. Effective nuclear charge increases
  • D. Atomic size always increases
Answer: C
Explanation: Increasing effective nuclear attraction makes electron removal progressively harder.

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

17. First ionisation enthalpy generally decreases down a group mainly because:

  • A. Electron affinity vanishes
  • B. Atomic size and shielding increase
  • C. Nuclear charge becomes zero
  • D. Valence electrons enter the same shell
Answer: B
Explanation: Greater distance and shielding weaken attraction for the outer electron.

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

18. Which generally has higher first ionisation enthalpy?

  • A. Mg than Na
  • B. Na than Mg
  • C. K than Na
  • D. Li than He
Answer: A
Explanation: Across Period 3, effective nuclear charge generally rises, so Mg has higher IE than Na.

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

19. The first ionisation enthalpy of Be is greater than B mainly because:

  • A. B has a filled 2p subshell
  • B. Be is larger than B
  • C. B is a noble gas
  • D. Be has a filled 2s subshell
Answer: D
Explanation: Removing B's 2p electron is easier than removing an electron from Be's stable filled 2s subshell.

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

20. The first ionisation enthalpy of N is greater than O mainly due to:

  • A. Complete p shell in N
  • B. Lower nuclear charge of O
  • C. Extra stability of half-filled 2p3 configuration
  • D. Larger size of N
Answer: C
Explanation: Nitrogen's half-filled p subshell is relatively stable; pairing in oxygen increases repulsion.

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