Classification of Elements and Periodicity — Class 11 MCQs with Answers
Class 11 CBSE Chemistry · Chapter 3
90 practice questions · 30 Easy · 30 Medium · 30 Hard · Updated
Practise the most important Class 11 CBSE Chemistry questions from Chapter 3, "Classification of Elements and Periodicity". You get 9 timed quizzes made from 90 NCERT-based MCQs, with answers and explanations. The questions are split into 30 Easy, 30 Medium and 30 Hard. Warm up on the basics, then move on to the exam-level questions that set top scorers in CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG apart.
To score well in "Classification of Elements and Periodicity", focus on reactions, key concepts and careful numericals. Each MCQ here is timed and uses exam-style marking (+4 correct, −1 wrong, 0 skipped). This trains you to stay accurate under time pressure, as real papers need. Every question has a short explanation, so a wrong answer becomes a quick lesson. It is the fastest way to fix gaps before a test.
Use this chapter for focused revision. Start with the Easy set to check your basics on Classification of Elements and Periodicity, then move to Medium and Hard to practise applying them. Your accuracy, streaks and XP save automatically. This chapter also adds to your overall Class 11 Chemistry mastery score. 14 sample questions are solved in full below, with the answer and a worked explanation. Sign in free to start practising.
Key concepts: Classification of Elements and Periodicity (Class 11 Chemistry)
This chapter arranges elements by the modern periodic law — properties are a periodic function of atomic number. It shows how s, p, d and f blocks arise from the last subshell filled, and how effective nuclear charge drives trends in atomic and ionic radius, ionisation and electron gain enthalpy, electronegativity and valence.
- Modern periodic law
- Properties of elements are a periodic function of their atomic number Z, not atomic mass; this repositioned anomalous pairs like Ar–K and Co–Ni correctly.
- Periods and groups
- The table has 7 periods and 18 groups; the period number equals the highest principal quantum number n in the atom, and fixes how many elements it holds.
- s-block elements
- Groups 1 and 2, filling the ns orbital; reactive metals that lose 1 or 2 electrons, form ionic compounds, and give strongly basic oxides.
- p-block elements
- Groups 13–18, filling np orbitals; spans metals, metalloids and non-metals, includes the halogens and noble gases, and shows varied oxidation states.
Classification of Elements and Periodicity — important questions & MCQs with answers (Class 11 Chemistry)
14 solved questions from this chapter's difficulty levels, each with its answer and explanation. The other 76 are timed and scored when you sign in.
- Q1Easy
Modern periodic table is arranged by:
A.Atomic massB.ColourC.DensityD.Atomic number✓ CorrectAnswer: D. Atomic number
Explanation: Moseley's X-ray spectra showed properties repeat periodically with atomic number Z, not atomic mass — so the modern table is arranged by Z. Picking atomic mass repeats Mendeleev's error, which misordered Ar (40 u) after K (39 u).
- Q2Easy
Across a period (left → right), electronegativity:
A.ZeroB.DecreasesC.ConstantD.Increases✓ CorrectAnswer: D. Increases
Explanation: Across a period, protons increase while the outer shell stays the same, so effective nuclear charge Zeff rises and pulls bonding electrons in harder — electronegativity increases left to right, e.g. Li 0.98 to F 3.98 (Pauling scale).
- Q3Easy
Modern periodic table has ___ groups.
A.18✓ CorrectB.7C.32D.8Answer: A. 18
Explanation: The modern table has 18 vertical columns (groups) and 7 horizontal rows (periods): 2 + 6 + 6 + 18 + 18 + 32 + 32 = 118 elements fit this grid. Confusing rows and columns gives the wrong count of 7.
- Q4Easy
Down a group, electronegativity:
A.Decreases✓ CorrectB.IncreasesC.ConstantD.RandomAnswer: A. Decreases
Explanation: Down a group, each new period adds a shell, so the outer electrons sit farther from the nucleus and are more shielded — the pull on bonding electrons weakens, so electronegativity decreases, e.g. F 3.98 down to I 2.66.
- Q5Easy
Number of periods in the modern periodic table:
A.18B.8C.6D.7✓ CorrectAnswer: D. 7
Explanation: Counting the horizontal rows from period 1 (H, He) to period 7 (Fr to Og) gives 7 periods total. 18 is the group count, not the period count — mixing rows with columns gives that wrong answer.
- Q6Easy
Across a period, atomic radius:
A.ConstantB.IncreasesC.Decreases✓ CorrectD.DoublesAnswer: C. Decreases
Explanation: Across a period, protons are added to the same shell, so Zeff rises and pulls the electron cloud inward — atomic radius decreases, e.g. Na 186 pm shrinks to Cl 99 pm. It does not stay constant or grow, since no new shell is added.
- Q7Medium
Element with configuration [Ar] 3d¹⁰ 4s² 4p³ belongs to:
A.f-blockB.d-block, group 5C.s-block, group 2D.p-block, group 15✓ CorrectAnswer: D. p-block, group 15
Explanation: For [Ar] 3d¹⁰ 4s² 4p³, the last electron enters a 4p orbital, so this is p-block; the group number for p-block equals 10 plus the s+p electron count, here 2 + 3 = 5, giving group 15. Stopping at the 3d¹⁰ count wrongly suggests d-block, group 5.
- Q8Medium
Down a group, atomic radius:
A.RandomB.DecreasesC.ConstantD.Increases✓ CorrectAnswer: D. Increases
Explanation: Down a group, each successive period adds a whole new principal shell (n increases by 1), pushing the outer electrons farther out despite the rising nuclear charge — so atomic radius increases, e.g. Li 152 pm to Cs 265 pm.
- Q9Medium
Element diagonally related to Li:
A.NaB.BeC.Mg✓ CorrectD.AlAnswer: C. Mg
Explanation: Diagonal relationships pair a period-2 element with the period-3 element one group to its right, since similar charge density gives similar chemistry: Li (group 1) pairs with Mg (group 2), Be pairs with Al. Picking Be or Na confuses the diagonal pair with same-group or same-period neighbours.
- Q10Medium
Across a period (left → right), ionisation energy:
A.Generally increases✓ CorrectB.DecreasesC.ConstantD.ZeroAnswer: A. Generally increases
Explanation: Across a period, Zeff rises steadily as electrons fill the same shell, pulling the valence electron in more tightly, so first ionisation energy generally increases, e.g. Li 520 kJ/mol up to Ne 2081 kJ/mol, with only minor dips at groups 2/13 and 15/16.
- Q11Medium
An element X has Z = 12. Its period and group:
A.Period 3, Group 2✓ CorrectB.Period 2, Group 12C.Period 3, Group 12D.Period 2, Group 2Answer: A. Period 3, Group 2
Explanation: Z = 12 is Mg with configuration [Ne] 3s². The valence shell is n = 3, giving period 3, and the s-subshell holds 2 electrons, giving group 2. Reading the shell number as the group (period 2, group 12) confuses n with group number.
- Q12Hard
Transition elements belong to:
A.s-blockB.d-block✓ CorrectC.p-blockD.f-blockAnswer: B. d-block
Explanation: Transition elements are defined by an incompletely filled (n−1)d subshell in the atom or a common ion, so their last electrons enter d orbitals, placing them squarely in the d-block, groups 3 through 12.
- Q13Hard
Most electronegative element:
A.ChlorineB.OxygenC.Fluorine✓ CorrectD.NitrogenAnswer: C. Fluorine
Explanation: Fluorine has the highest electronegativity of any element, 3.98 on the Pauling scale, because its small 2p valence shell combined with high effective nuclear charge pulls bonding electrons in more strongly than oxygen (3.44), chlorine (3.16), or nitrogen (3.04) can manage.
- Q14Hard
Element with Z = 24 belongs to:
A.p-block, group 4B.d-block, group 4C.d-block, group 6✓ CorrectD.f-blockAnswer: C. d-block, group 6
Explanation: Chromium (Z=24) has the anomalous configuration [Ar] 3d⁵ 4s¹ (a stable half-filled d subshell, not the expected 3d⁴4s²), so its last electron enters 3d, making it d-block; group number = d-electrons + s-electrons = 5 + 1 = 6, not group 4.
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Start this chapter free →Classification of Elements and Periodicity — FAQs
What are the key concepts in Class 11 Chemistry Classification of Elements and Periodicity?+
This chapter arranges elements by the modern periodic law — properties are a periodic function of atomic number. It shows how s, p, d and f blocks arise from the last subshell filled, and how effective nuclear charge drives trends in atomic and ionic radius, ionisation and electron gain enthalpy, electronegativity and valence. Key ideas include Modern periodic law, Periods and groups, s-block elements, p-block elements.
What does Class 11 Chemistry Chapter 3 (Classification of Elements and Periodicity) cover on XamBaaz?+
It has 90 NCERT-based MCQs on "Classification of Elements and Periodicity": 30 Easy, 30 Medium and 30 Hard. Together they make 9 timed quizzes, and you never get the same set twice. Every question has an instant explanation. They help you prepare for CBSE & Maharashtra HSC Board exams, JEE Main, MHT-CET, JEE Advanced and NEET UG.
Are these "Classification of Elements and Periodicity" questions free to practise?+
Yes. Sign in with Google to practise "Classification of Elements and Periodicity" free. Full unlimited access is ₹999/year on a launch offer until 1 December 2026. No chapter is charged separately.
How should I revise "Classification of Elements and Periodicity" for the exam?+
Start with the Easy quiz to check your basics, then try Medium and Hard to practise applying them. There are 9 timed quizzes on this chapter, so you can come back for a fresh set instead of one you have seen. Read each explanation, retry the questions you miss, and track your accuracy until it stays high.
Are these "Classification of Elements and Periodicity" MCQs available with answers?+
Yes. 14 sample questions are shown here in full, each with the correct option and a step-by-step "Why" explanation. Sign in free with Google to start practising, with instant scoring.
Is there negative marking in the "Classification of Elements and Periodicity" quizzes?+
Yes. The timed quizzes use exam-style marking: +4 for a right answer, −1 for a wrong one and 0 for a skip, the same negative marking as JEE Main, JEE Advanced and NEET UG. MHT-CET and CBSE board papers have no negative marking. Our mocks for those are scored their way.
What are the important questions from Classification of Elements and Periodicity (Class 11 Chemistry)?+
The questions that matter most test Modern periodic law, Periods and groups, s-block elements, p-block elements. This page shows 14 solved important MCQs with answers and explanations; all 90 questions on the chapter are available as timed quizzes once you sign in.
Is there an online quiz for Classification of Elements and Periodicity?+
Yes — Class 11 Chemistry Classification of Elements and Periodicity has timed online quizzes at Easy, Medium and Hard levels, with instant scoring and a worked explanation on every question. The first quiz on the chapter is free.