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Classification of Elements and Periodicity in Properties NEET MCQ & Practice Questions

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Classification of Elements and Periodicity in Properties Revision Guide for NEET Chemistry

Classification of Elements and Periodicity in Properties is part of NEET 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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NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

1. Which order of atomic radii is correct for Period 3 elements?

  • A. Na > Al > Mg > Si
  • B. Mg > Na > Al > Si
  • C. Na > Mg > Al > Si
  • D. Si > Al > Mg > Na
Answer: C
Explanation: Across a period, effective nuclear charge increases while electrons enter the same shell, so atomic radius generally decreases.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

2. Which species has the smallest ionic radius?

  • A. Mg2+
  • B. O2−
  • C. F−
  • D. Na+
Answer: A
Explanation: All four species are isoelectronic with 10 electrons. The species with the greatest nuclear charge, Mg2+, has the smallest radius.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

3. Which order of first ionisation enthalpy is correct?

  • A. B < Be < C < N
  • B. Be < B < C < N
  • C. B < C < Be < N
  • D. C < B < Be < N
Answer: A
Explanation: B has lower ionisation enthalpy than Be because its electron is removed from a higher-energy 2p orbital. The general increase then gives B < Be < C < N.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

4. Why is the first ionisation enthalpy of oxygen lower than that of nitrogen?

  • A. Oxygen has paired electrons in a 2p orbital, increasing repulsion
  • B. Nitrogen has fewer protons
  • C. Oxygen has a half-filled p subshell
  • D. Oxygen has a larger atomic radius
Answer: A
Explanation: Nitrogen has a stable half-filled 2p3 configuration, while oxygen has one paired 2p orbital, making electron removal easier.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

5. Which element has the most negative electron gain enthalpy?

  • A. Br
  • B. I
  • C. F
  • D. Cl
Answer: D
Explanation: Chlorine has a more negative electron gain enthalpy than fluorine because the compact 2p shell of fluorine causes greater electron-electron repulsion.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

6. Which order of electronegativity is correct?

  • A. F > N > O > C
  • B. F > O > N > C
  • C. C > N > O > F
  • D. O > F > N > C
Answer: B
Explanation: Electronegativity increases across Period 2, giving C < N < O < F.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

7. Which oxide is the most acidic?

  • A. Na2O
  • B. MgO
  • C. Al2O3
  • D. Cl2O7
Answer: D
Explanation: Across a period, metallic character decreases and oxide acidity increases. Cl2O7 is a strongly acidic oxide.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

8. Which oxide is amphoteric?

  • A. MgO
  • B. Al2O3
  • C. SiO2
  • D. Na2O
Answer: B
Explanation: Al2O3 reacts with both acids and bases, so it is amphoteric.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

9. Which order of metallic character is correct?

  • A. Al > Mg > Na > Si
  • B. Mg > Na > Si > Al
  • C. Na > Mg > Al > Si
  • D. Si > Al > Mg > Na
Answer: C
Explanation: Metallic character decreases from left to right across Period 3.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

10. Which element has the highest second ionisation enthalpy?

  • A. Si
  • B. Na
  • C. Mg
  • D. Al
Answer: B
Explanation: After losing one electron, Na+ has the stable noble-gas configuration [Ne]. Removing a second electron therefore requires very high energy.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

11. Which pair shows a diagonal relationship?

  • A. Li and Mg
  • B. Na and Mg
  • C. Be and B
  • D. B and C
Answer: A
Explanation: Lithium resembles magnesium due to similar charge density and polarising power, producing a diagonal relationship.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

12. Which statement best explains the inert-pair effect?

  • A. The np electrons become completely inert
  • B. All valence electrons participate equally down a group
  • C. It occurs only in s-block elements
  • D. The ns2 electrons become increasingly reluctant to participate in bonding down a p-block group
Answer: D
Explanation: Poor shielding by intervening d and f electrons increases effective nuclear attraction for ns2 electrons, making them less available for bonding.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

13. Which element has the highest electron affinity among the following?

  • A. F
  • B. Ne
  • C. N
  • D. O
Answer: A
Explanation: Fluorine strongly attracts an added electron; nitrogen has a stable half-filled configuration and neon has a closed shell.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

14. Which order of ionic radii is correct?

  • A. O2− > N3− > F− > Na+
  • B. N3− > O2− > F− > Na+
  • C. Na+ > F− > O2− > N3−
  • D. F− > O2− > N3− > Na+
Answer: B
Explanation: These are isoelectronic species. Radius decreases as nuclear charge increases: N3− > O2− > F− > Na+.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

15. Which period contains the maximum number of elements?

  • A. Second
  • B. Third
  • C. Fourth
  • D. Sixth
Answer: D
Explanation: The sixth period contains 32 elements, including the lanthanoids.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

16. The general valence-shell configuration of halogens is:

  • A. ns2np4
  • B. ns1
  • C. ns2
  • D. ns2np5
Answer: D
Explanation: Group 17 elements have seven valence electrons with configuration ns2np5.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

17. Which element is expected to show the greatest covalent character in its chloride?

  • A. Al
  • B. Si
  • C. Na
  • D. Mg
Answer: B
Explanation: Higher charge and smaller size increase polarising power. SiCl4 is molecular and strongly covalent.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

18. Which chloride is expected to have the greatest ionic character?

  • A. AlCl3
  • B. LiCl
  • C. NaCl
  • D. BeCl2
Answer: C
Explanation: Na+ has lower polarising power than Li+, Be2+ and Al3+, so NaCl is the most ionic.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

19. Which order of hydration enthalpy magnitude is correct?

  • A. Li+ > Na+ > K+ > Rb+
  • B. Rb+ > K+ > Na+ > Li+
  • C. Na+ > Li+ > K+ > Rb+
  • D. K+ > Na+ > Li+ > Rb+
Answer: A
Explanation: Hydration enthalpy magnitude decreases with increasing ionic radius. Li+ is smallest and most strongly hydrated.

NEET Chemistry · Classification of Elements and Periodicity in Properties · Very Hard

20. Which alkali metal has the lowest melting point?

  • A. Na
  • B. K
  • C. Cs
  • D. Li
Answer: C
Explanation: Metallic bonding weakens down Group 1 as atomic size increases, so caesium has the lowest melting point among these.

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