MCQs for Class 10 Science Chapter 5 Periodic Classification of Elements

Periodic Classification of Elements is an important chapter in Class 10 Science that helps students understand the modern periodic table, Mendeleev’s classification, groups, periods, valency, and periodic trends in atomic size. Practicing Periodic Classification of Elements Class 10 MCQs helps students strengthen conceptual understanding, improve accuracy, and prepare for competency-based questions in CBSE board exams.

Students can revise important concepts through chapter-wise Class 10 Science MCQs and explore CBSE Board resources for exam preparation. For practice across different subjects, the Class 10 MCQs collection and the complete MCQs section provide additional objective questions to support regular revision and better preparation.

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MCQs for Class 10 Science Chapter 5 with Answers and Explanations 

Need more practice in Periodic Classification of Elements? Solve these Class 10 Science MCQs to revise important topics before your exams.. This section covers important concepts like modern periodic law, Mendeleev periodic table, periodic trends, groups and periods, assertion-reason questions, and competency-based board exam practice.

Q1. Henry Moseley demonstrated that a fundamental property of an element can be used to organize the periodic table more effectively than atomic mass. Identify this property.

A. Total number of nucleons
B. Number of protons in the nucleus
C. Number of neutrons in the core
D. Total number of stable isotopes

Answer: B. Number of protons in the nucleus

Explanation: Moseley discovered that atomic number, which represents the number of protons in the nucleus, is the correct basis for arranging elements in the periodic table.

Q2. A student analyzes a highly reactive non-metal located at the top of the halogen group. Which element matches this description?

A. Fluorine
B. Oxygen
C. Chlorine
D. Sodium

Answer: A. Fluorine

Explanation: Fluorine is the most reactive non-metal because of its very small atomic size and high electronegativity.

Q3. Consider the elements Nitrogen, Oxygen, and Fluorine, which all belong to the second period. Choose the correct increasing order of atomic size.

A. Nitrogen < Oxygen < Fluorine
B. Fluorine < Oxygen < Nitrogen
C. Oxygen < Nitrogen < Fluorine
D. Fluorine < Nitrogen < Oxygen

Answer: B. Fluorine < Oxygen < Nitrogen

Explanation: Atomic size decreases from left to right across a period because nuclear charge increases.

Q4. An unknown element X forms a chloride with the formula XCl2. In which group is X most likely placed?

A. Group 1
B. Group 13
C. Group 2
D. Group 14

Answer: C. Group 2

Explanation: The formula XCl2 shows that X has valency 2, which is characteristic of Group 2 elements.

Q5. How does electropositive character change from left to right across Period 3?

A. It steadily decreases
B. It first increases, then decreases
C. It steadily increases
D. It remains unchanged

Answer: A. It steadily decreases

Explanation: Across a period, effective nuclear charge increases, making it harder for atoms to lose electrons.

Q6. What is the main characteristic of Group 18 elements?

A. One electron in the outermost shell
B. Completely filled valence shell
C. Formation of diatomic molecules
D. High tendency to form ionic compounds

Answer: B. Completely filled valence shell

Explanation: Noble gases have completely filled outermost shells, making them chemically stable and less reactive.

Q7. Groups 3 to 12 in the periodic table are known as:

A. Representative elements
B. Lanthanides
C. Transition elements
D. Main-group non-metals

Answer: C. Transition elements

Explanation: These elements have partially filled d-orbitals and are called transition elements.

Q8. An element M has electronic configuration 2, 8, 4. Identify its group.

A. Group 4
B. Group 14
C. Group 2
D. Group 12

Answer: B. Group 14

Explanation: The element has 4 valence electrons. For p-block elements, group number = valence electrons + 10. Therefore, 4 + 10 = 14.

Q9. Which element has exactly two completely filled energy levels?

A. Helium
B. Argon
C. Neon
D. Krypton

Answer: C. Neon

Explanation: Neon has electronic configuration 2, 8, with both shells completely filled.

Q10. What was one major success of Mendeleev’s periodic table?

A. Prediction of properties of undiscovered elements
B. Prediction that no elements exist after Uranium
C. Calculation of radioactive decay rates
D. Prediction that all missing elements are noble gases

Answer: A. Prediction of properties of undiscovered elements

Explanation: Mendeleev predicted properties of undiscovered elements such as Gallium and Germanium.

Q11. What trend is observed in atomic radius from Sodium to Chlorine?

A. Atomic radius increases
B. Atomic radius decreases
C. Atomic radius remains constant
D. Atomic radius changes irregularly

Answer: B. Atomic radius decreases

Explanation: Increasing nuclear charge across the period pulls electrons closer to the nucleus.

Q12. How does Boron generally achieve stability?

A. By losing 3 electrons
B. By sharing 3 electrons
C. By gaining 5 electrons
D. By forming metallic bonds only

Answer: B. By sharing 3 electrons

Explanation: Boron mainly forms covalent compounds by sharing electrons.

Q13. How does electronegativity change from left to right across a period?

A. It decreases
B. It increases
C. It remains constant
D. It fluctuates randomly

Answer: B. It increases

Explanation: Atomic size decreases and nuclear attraction increases across a period.

Q14. Why does metallic character increase down Group 1?

A. Nuclear charge decreases
B. Valence electrons move farther from the nucleus
C. Number of valence electrons changes
D. Atomic size decreases

Answer: B. Valence electrons move farther from the nucleus

Explanation: Increased shielding and atomic size make electron loss easier.

Q15. How does valency vary across the second period?

A. It increases from 1 to 8
B. It decreases from 7 to 1
C. It increases from 1 to 4, then decreases to 0
D. It remains 2 throughout

Answer: C. It increases from 1 to 4, then decreases to 0

Explanation: Valency first increases up to Group 14, then decreases toward noble gases.

Q16. The 14 elements following Actinium are called:

A. Lanthanides
B. Transition metals
C. Actinides
D. Chalcogens

Answer: C. Actinides

Explanation: These are f-block elements in which the 5f orbitals are progressively filled.

Q17. An element with atomic number 15 will show properties similar to:

A. Beryllium
B. Neon
C. Nitrogen
D. Oxygen

Answer: C. Nitrogen

Explanation: Both elements have 5 valence electrons and belong to the same group.

Q18. An element with atomic number 8 belongs to:

A. Group 6, Period 2
B. Group 16, Period 2
C. Group 16, Period 4
D. Group 8, Period 2

Answer: B. Group 16, Period 2

Explanation: Oxygen has electronic configuration 2, 6, so it belongs to Group 16 and Period 2.

Q19. An element in Group 2 and Period 2 has how many valence electrons?

A. 2
B. 4
C. 1
D. 8

Answer: A. 2

Explanation: Group 2 elements contain 2 electrons in their outermost shell.

Q20. Which element in Period 3 has the smallest atomic volume excluding noble gases?

A. Sodium
B. Silicon
C. Chlorine
D. Argon

Answer: C. Chlorine

Explanation: Chlorine experiences the highest effective nuclear charge among non-noble gas elements in Period 3.

Q21. What is the electronic configuration of Al3+?

A. 2, 8, 3
B. 2, 8
C. 2, 8, 8
D. 2, 4

Answer: B. 2, 8

Explanation: Aluminium loses 3 electrons to form Al3+, leaving a stable configuration of 2, 8.

Q22. Which set is NOT a Dobereiner Triad?

A. Lithium, Sodium, Potassium
B. Calcium, Strontium, Barium
C. Chlorine, Bromine, Iodine
D. Beryllium, Magnesium, Chromium

Answer: D. Beryllium, Magnesium, Chromium

Explanation: These elements neither belong to the same group nor follow the triad relationship.

Q23. Which statement about noble gases is correct?

A. They are radioactive liquids
B. They exist as monoatomic gases
C. They form strong ionic bonds easily
D. They have very low ionization energy

Answer: B. They exist as monoatomic gases

Explanation: Noble gases have stable electronic configurations and exist independently as single atoms.

Q24. Which sequence represents an incorrect vertical group arrangement?

A. Nitrogen, Phosphorus, Arsenic
B. Copper, Silver, Gold
C. Calcium, Bromine, Barium
D. Chlorine, Bromine, Iodine

Answer: C. Calcium, Bromine, Barium

Explanation: Calcium and Barium belong to Group 2, whereas Bromine belongs to Group 17.

Q25. An element forms an oxide that turns red litmus blue. What is a likely atomic number of the element?

A. 7
B. 17
C. 11
D. 14

Answer: C. 11

Explanation: Sodium (atomic number 11) forms sodium oxide (Na2O), which is basic in nature.

Q26. An element has electronic configuration 1s2 2s2 2p6 3s1. Which statement is incorrect?

A. It reacts with water to form a hydroxide
B. It behaves as a non-metal with high electron affinity
C. It has valency 1
D. It forms a univalent positive ion

Answer: B. It behaves as a non-metal with high electron affinity

Explanation: The configuration belongs to Sodium, which is a highly reactive metal.

Q27. Which groups contain s-block elements?

A. Groups 13 and 14
B. Groups 1 and 2
C. Groups 15 and 16
D. Groups 17 and 18

Answer: B. Groups 1 and 2

Explanation: s-block elements have valence electrons in the s-orbital.

Q28. An element has electronic configuration 1s2 2s2 2p6 3s2 3p4. Identify its group.

A. Group 4
B. Group 6
C. Group 16
D. Group 14

Answer: C. Group 16

Explanation: The element has 6 valence electrons, so its group number is 16.

Q29. Which ion has the smallest ionic radius?

A. Na+
B. Mg2+
C. Al3+
D. K+

Answer: C. Al3+

Explanation: Al3+ has the highest nuclear charge among these ions, pulling electrons closer to the nucleus.

Q30. Up to which element was Newlands’ Law of Octaves applicable?

A. Oxygen
B. Potassium
C. Calcium
D. Cobalt

Answer: C. Calcium

Explanation: Newlands’ Law of Octaves worked correctly only up to Calcium.

Quick Chapter Overview

The chapter Periodic Classification of Elements explains how scientists arranged elements based on similarities in their properties. Students learn about Dobereiner Triads, Newlands Law of Octaves, Mendeleev’s periodic table, the modern periodic law, and periodic trends like atomic size, valency, and metallic character.

This chapter is important because many board exam questions are directly based on trends and concept application.

What You’ll Practice in These MCQs

Important Exam Focus Areas

Students should focus more on:

• modern periodic law
• atomic number based classification
• trends in atomic size
• metallic and non-metallic character
• valency trends
• Mendeleev achievements and limitations
• difference between groups and periods

These concepts are commonly asked in MCQs, assertion-reason, and competency-based questions.