Timer: Off
Random: Off
1. Who is credited with the first attempt to classify elements systematically?
ⓐ. Lavoisier
ⓑ. Dobereiner
ⓒ. Newlands
ⓓ. Mendeleev
Correct Answer: Dobereiner
Explanation: In 1817, Johann Dobereiner grouped elements into “triads” based on similar properties and atomic masses. For example, the triad of calcium, strontium, and barium showed that the atomic mass of strontium was nearly the average of calcium and barium. Although limited, this was the first scientific attempt to classify elements.
2. What was the basis of Mendeleev’s periodic table?
ⓐ. Atomic number
ⓑ. Valency only
ⓒ. Atomic mass
ⓓ. Electronegativity
Correct Answer: Atomic mass
Explanation: Mendeleev in 1869 arranged elements in increasing order of atomic mass. He observed periodic repetition of properties and left gaps for undiscovered elements. Later, modern periodic law modified the basis from atomic mass to atomic number.
3. Who gave the modern periodic law?
ⓐ. Mendeleev
ⓑ. Moseley
ⓒ. Dalton
ⓓ. Rutherford
Correct Answer: Moseley
Explanation: Henry Moseley in 1913 showed that atomic number (nuclear charge) is a better fundamental property than atomic mass. He established the modern periodic law: “Properties of elements are a periodic function of their atomic numbers.”
4. The horizontal rows in the modern periodic table are called:
ⓐ. Groups
ⓑ. Periods
ⓒ. Blocks
ⓓ. Families
Correct Answer: Periods
Explanation: The periodic table has 7 periods (horizontal rows) and 18 groups (vertical columns). Periods correspond to the filling of successive electron shells (n = 1 to 7). Groups contain elements with similar valence electron configurations.
5. How many elements are present in the second period of the modern periodic table?
ⓐ. 2
ⓑ. 8
ⓒ. 18
ⓓ. 32
Correct Answer: 8
Explanation: The second period corresponds to filling of the n=2 shell (2s and 2p orbitals). Hence, it contains 8 elements (Lithium to Neon). This is called a “short period.”
6. Which block elements are called transition elements?
ⓐ. s-block
ⓑ. p-block
ⓒ. d-block
ⓓ. f-block
Correct Answer: d-block
Explanation: Transition elements belong to the d-block, where the last electron enters a d-orbital. They show variable oxidation states, colored compounds, and catalytic properties. Examples include Fe, Cu, Ni, etc.
7. Which block contains the inner transition elements?
ⓐ. s-block
ⓑ. p-block
ⓒ. d-block
ⓓ. f-block
Correct Answer: f-block
Explanation: Inner transition elements are the lanthanides and actinides. They belong to the f-block, where electrons fill the f-orbitals. They are usually placed separately below the main table to maintain compactness.
8. Which element is known as the “bridge element” between s-block and p-block?
ⓐ. Hydrogen
ⓑ. Helium
ⓒ. Beryllium
ⓓ. Boron
Correct Answer: Helium
Explanation: Helium has electronic configuration 1s² (like s-block), but is placed in group 18 (p-block) because of its inert gas properties. Thus, it acts as a bridge between s and p-block classifications.
9. The maximum number of elements present in the 6th period of the periodic table is:
ⓐ. 18
ⓑ. 32
ⓒ. 8
ⓓ. 50
Correct Answer: 32
Explanation: The 6th period includes the filling of 6s, 4f, 5d, and 6p orbitals. Thus, it contains 32 elements (including lanthanides). It is the longest period in the periodic table.
10. What is the correct order of discovery in classification of elements?
ⓐ. Newlands → Dobereiner → Mendeleev → Moseley
ⓑ. Dobereiner → Newlands → Mendeleev → Moseley
ⓒ. Mendeleev → Dobereiner → Newlands → Moseley
ⓓ. Moseley → Newlands → Dobereiner → Mendeleev
Correct Answer: Dobereiner → Newlands → Mendeleev → Moseley
Explanation: The classification began with Dobereiner’s Triads (1817), followed by Newlands’ Law of Octaves (1864), then Mendeleev’s Periodic Table (1869), and finally Moseley’s Modern Periodic Law (1913). Each step corrected or improved upon the previous system.
11. By the early 19th century, about how many elements were known to chemists?
ⓐ. Around 20
ⓑ. Around 33
ⓒ. Around 60
ⓓ. Around 100
Correct Answer: Around 33
Explanation: Antoine Lavoisier in 1789 published a list of 33 known elements in his book *Traité Élémentaire de Chimie*. This was one of the earliest systematic compilations. The number later kept increasing as new elements were discovered.
12. By the mid-19th century, approximately how many elements had been discovered?
ⓐ. 33
ⓑ. 63
ⓒ. 80
ⓓ. 100
Correct Answer: 63
Explanation: By 1869, when Mendeleev proposed his periodic table, 63 elements were known. This made classification a necessity since properties were becoming difficult to study individually.
13. Which scientist in 1789 attempted one of the earliest classifications of 33 elements into metals and non-metals?
ⓐ. Dalton
ⓑ. Lavoisier
ⓒ. Mendeleev
ⓓ. Newlands
Correct Answer: Lavoisier
Explanation: Antoine Lavoisier classified known substances as metals and non-metals. Though crude, it was a first step in recognizing differences among elements. Later refinements used atomic mass and properties.
14. Why did the increasing number of elements demand systematic classification?
ⓐ. To make the periodic table more colorful
ⓑ. To predict and understand properties logically
ⓒ. To reduce the number of discovered elements
ⓓ. To avoid the use of atomic numbers
Correct Answer: To predict and understand properties logically
Explanation: As elements increased from a few dozen to over 60, studying them individually became complex. Classification grouped elements by similar properties, making learning easier and enabling prediction of new elements.
15. Who compiled the first list of elements with symbols and atomic weights, aiding in classification?
ⓐ. Newlands
ⓑ. Berzelius
ⓒ. Rutherford
ⓓ. Moseley
Correct Answer: Berzelius
Explanation: Jöns Jacob Berzelius in the early 19th century introduced modern symbols and determined atomic weights of many elements. This information was crucial for later periodic classification systems.
16. Approximately how many naturally occurring elements are known today?
ⓐ. 63
ⓑ. 92
ⓒ. 100
ⓓ. 118
Correct Answer: 92
Explanation: 92 elements occur naturally (from hydrogen to uranium). Elements beyond uranium are synthetic and created in laboratories. The total count today is 118 elements recognized by IUPAC.
17. Which was the first element discovered in the 20th century?
ⓐ. Argon
ⓑ. Radon
ⓒ. Technetium
ⓓ. Francium
Correct Answer: Technetium
Explanation: Technetium (atomic number 43) was the first artificially synthesized element in 1937. It filled a gap predicted by Mendeleev. Discovery of such elements expanded the periodic table beyond naturally occurring elements.
18. Why was classification based only on metals and non-metals insufficient?
ⓐ. Because most elements were metals
ⓑ. Because some elements showed dual properties
ⓒ. Because it ignored atomic mass trends
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Simply dividing elements as metals or non-metals failed since many elements (e.g., metalloids) showed dual behavior. It also did not explain periodic properties or trends in reactivity. Hence, more systematic classification was required.
19. During which period of history did the number of known elements grow rapidly due to improved experimental techniques?
ⓐ. 16th century
ⓑ. 17th century
ⓒ. 18th century
ⓓ. 19th century
Correct Answer: 19th century
Explanation: In the 19th century, advancements in experimental chemistry and analytical methods (spectroscopy, electrolysis) led to rapid discovery of many elements such as alkali metals and transition metals, increasing the need for classification.
20. Which of the following is true about the growth in the number of elements?
ⓐ. Elements stopped being discovered after Mendeleev
ⓑ. New synthetic elements have been added beyond uranium
ⓒ. Only non-metals were discovered after 1900
ⓓ. All elements were known before 1800
Correct Answer: New synthetic elements have been added beyond uranium
Explanation: After uranium (Z=92), heavier elements were synthesized in labs. Examples include neptunium, plutonium, and even superheavy elements like oganesson (Z=118). This shows classification systems had to be flexible to incorporate new discoveries.
21. Which was the simplest way of grouping elements in early classifications?
ⓐ. By atomic number
ⓑ. By similar properties
ⓒ. By alphabetical order
ⓓ. By atomic weights
Correct Answer: By similar properties
Explanation: Before atomic number was discovered, chemists grouped elements mainly based on similar physical and chemical properties. For example, halogens (Cl, Br, I) were grouped together due to common salt-forming behavior.
22. Which of the following sets of elements was grouped together due to similar properties?
ⓐ. H, O, N
ⓑ. Na, K, Rb
ⓒ. C, Si, P
ⓓ. Cu, Ag, Zn
Correct Answer: Na, K, Rb
Explanation: Alkali metals (Na, K, Rb) were grouped because of their highly reactive nature, tendency to form +1 cations, and similar reactions with water. Grouping was based on patterns of reactivity.
23. Which scientist first grouped elements into metals and non-metals?
ⓐ. Dobereiner
ⓑ. Berzelius
ⓒ. Lavoisier
ⓓ. Mendeleev
Correct Answer: Lavoisier
Explanation: In 1789, Lavoisier classified 33 known elements broadly into metals and non-metals. Although oversimplified, it recognized the need for grouping based on shared chemical properties.
24. Which group of elements was historically called “halogens” due to similar salt-forming properties?
ⓐ. Group 14 elements
ⓑ. Group 15 elements
ⓒ. Group 16 elements
ⓓ. Group 17 elements
Correct Answer: Group 17 elements
Explanation: Chlorine, bromine, iodine, and fluorine were grouped as halogens, meaning “salt producers,” since they readily combine with metals to form salts such as NaCl and KBr.
25. Why was grouping by similar properties considered useful?
ⓐ. It explained isotopes
ⓑ. It allowed prediction of behavior of new elements
ⓒ. It reduced the number of known elements
ⓓ. It eliminated the need for atomic weights
Correct Answer: It allowed prediction of behavior of new elements
Explanation: Grouping allowed chemists to study families of elements rather than each individually. If an element shared properties with a group, its behavior could be predicted even before all properties were known.
26. Which set of elements was grouped together due to noble gas inertness?
ⓐ. Li, Na, K
ⓑ. Cl, Br, I
ⓒ. He, Ne, Ar
ⓓ. Fe, Co, Ni
Correct Answer: He, Ne, Ar
Explanation: Noble gases (He, Ne, Ar) were grouped together once discovered, as they showed complete chemical inertness due to filled outer shells. Their grouping was purely based on lack of reactivity.
27. Which property was mostly used by early chemists to group elements?
ⓐ. Atomic mass
ⓑ. Valency
ⓒ. Radioactivity
ⓓ. Color of compounds
Correct Answer: Valency
Explanation: Elements with the same valency were grouped together as they formed similar types of compounds. For example, alkali metals (valency +1) and alkaline earth metals (valency +2).
28. Which of the following groups of elements shows similar reactivity with water?
ⓐ. Na, K, Rb
ⓑ. O, S, Se
ⓒ. Cu, Ag, Au
ⓓ. N, P, As
Correct Answer: Na, K, Rb
Explanation: Alkali metals react vigorously with water to form hydroxides and hydrogen gas. Their grouping highlighted this shared reactivity, helping establish periodic trends later.
29. Which common property groups halogens together?
ⓐ. They all are metals
ⓑ. They form diatomic molecules and salts with metals
ⓒ. They are noble gases
ⓓ. They have valency zero
Correct Answer: They form diatomic molecules and salts with metals
Explanation: Halogens exist as diatomic molecules (Cl₂, Br₂, I₂) and combine with metals to form salts like NaCl, KBr. This salt-forming property was key in grouping them together.
30. Which was a major limitation of grouping elements only by similar properties?
ⓐ. It ignored isotopes
ⓑ. It could not explain increasing atomic mass trends
ⓒ. Some elements showed properties of two groups
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Grouping by properties alone was insufficient since some elements (like metalloids) showed dual properties, isotopes were not explained, and trends like atomic mass were ignored. This led to the search for more systematic classifications.
31. Why was random classification of elements considered unsatisfactory?
ⓐ. It was too simple to remember
ⓑ. It grouped isotopes together
ⓒ. It lacked a scientific basis and order
ⓓ. It used atomic number instead of mass
Correct Answer: It lacked a scientific basis and order
Explanation: Random classification like metals vs. non-metals was not based on a fundamental property. It did not explain periodicity, similarities, or predict new elements, making it unsatisfactory for scientific study.
32. Which major drawback arose when elements were grouped only as metals and non-metals?
ⓐ. Some metals were missing
ⓑ. Elements showing both metallic and non-metallic properties could not be placed
ⓒ. Too many elements were non-metals
ⓓ. Atomic weights were ignored
Correct Answer: Elements showing both metallic and non-metallic properties could not be placed
Explanation: Metalloids (e.g., B, Si, As) show properties of both metals and non-metals. Random classification could not accommodate such elements, reducing its reliability.
33. Why could random classification not help in predicting new elements?
ⓐ. Because it was not based on atomic structure
ⓑ. Because it depended only on atomic number
ⓒ. Because elements were not increasing
ⓓ. Because isotopes were not known
Correct Answer: Because it was not based on atomic structure
Explanation: Random classification lacked a systematic approach like atomic mass or number. Therefore, it failed to predict the discovery of new elements, unlike Mendeleev’s table.
34. Which property was completely ignored in random classifications?
ⓐ. Atomic number
ⓑ. Periodic trends
ⓒ. Isotopes
ⓓ. Electron affinity
Correct Answer: Periodic trends
Explanation: Random classification did not recognize periodicity—the repetition of properties at regular intervals. This was a crucial weakness since periodicity is the foundation of modern classification.
35. Which of the following is an example of misplacement in random classification?
ⓐ. Hydrogen placed with alkali metals
ⓑ. Halogens with noble gases
ⓒ. Carbon grouped with nitrogen
ⓓ. Oxygen placed with alkali metals
Correct Answer: Hydrogen placed with alkali metals
Explanation: Hydrogen shares some properties with alkali metals but also with halogens. Random classification failed to assign it a proper place, highlighting its limitations.
36. What was the problem with classifying elements only based on physical states?
ⓐ. It was too easy to classify gases
ⓑ. Many elements change state under conditions
ⓒ. It separated metals from non-metals
ⓓ. It used modern periodic law
Correct Answer: Many elements change state under conditions
Explanation: Elements exist in different states depending on temperature and pressure (e.g., bromine is liquid, iodine is solid, chlorine is gas). Thus, state-based classification was unreliable.
37. Why was the classification of elements into families without considering atomic mass problematic?
ⓐ. It ignored valency
ⓑ. It placed unlike elements together
ⓒ. It didn’t account for isotopes
ⓓ. It considered atomic numbers
Correct Answer: It placed unlike elements together
Explanation: Without atomic mass trends, unrelated elements could be grouped incorrectly. For example, nitrogen and sodium could both be classified simply as “non-metals” or “metals,” ignoring their vast chemical differences.
38. Which important scientific principle was missing from random classification?
ⓐ. Relation between atomic mass and properties
ⓑ. Isotopic abundance
ⓒ. Discovery of protons
ⓓ. Electron configuration
Correct Answer: Relation between atomic mass and properties
Explanation: Early random grouping failed to see that properties are linked with atomic structure (mass/number). Mendeleev and Moseley later solved this by using atomic mass and atomic number, respectively.
39. Why did classification purely on valency fail?
ⓐ. Because all elements had the same valency
ⓑ. Because some elements showed variable valency
ⓒ. Because isotopes did not exist
ⓓ. Because noble gases were unknown
Correct Answer: Because some elements showed variable valency
Explanation: Elements like Fe (+2, +3), Cu (+1, +2), and Sn (+2, +4) exhibit variable valency. Random classification could not explain such cases, limiting its accuracy.
40. Which of the following best summarizes the limitation of random classification?
ⓐ. It ignored isotopes only
ⓑ. It was too advanced for its time
ⓒ. It did not reflect atomic structure or periodicity
ⓓ. It used atomic number instead of atomic mass
Correct Answer: It did not reflect atomic structure or periodicity
Explanation: The key weakness of random classification was the absence of a link with atomic structure and periodic law. Without a periodic framework, classification was arbitrary and scientifically weak.
41. What was the main idea behind Döbereiner’s Triads?
ⓐ. Elements were arranged in order of atomic number.
ⓑ. Properties of the middle element were the average of the other two.
ⓒ. Elements were classified into metals and non-metals.
ⓓ. Elements were grouped according to color of compounds.
Correct Answer: Properties of the middle element were the average of the other two.
Explanation: In 1817, Johann Wolfgang Döbereiner grouped elements into sets of three called *triads*. He noticed that the atomic mass and some properties of the middle element were approximately the average of the other two. For example, in the triad of calcium (40), strontium (88), and barium (137), the atomic mass of strontium (\~88) is close to the mean of calcium and barium $(40+137)/2=88.5$. This showed an early hint of periodicity, though limited to a few sets.
42. Which of the following is an example of Döbereiner’s Triad?
ⓐ. Li, Na, K
ⓑ. C, N, O
ⓒ. H, He, Ne
ⓓ. Fe, Cu, Zn
Correct Answer: Li, Na, K
Explanation: Lithium (7), sodium (23), and potassium (39) form a triad. The average of the atomic masses of lithium and potassium $(7+39)/2=23$ is nearly equal to sodium’s atomic mass (23). Their properties like reactivity and formation of +1 ions are also similar. This demonstrated a systematic relationship between atomic masses and properties.
43. How many triads were originally proposed by Döbereiner?
ⓐ. 2
ⓑ. 3
ⓒ. 5
ⓓ. 8
Correct Answer: 5
Explanation: Döbereiner identified 5 triads, including alkali metals (Li, Na, K), alkaline earth metals (Ca, Sr, Ba), and halogens (Cl, Br, I). Each triad displayed the “law of triads” where the middle element’s properties were intermediate and its atomic mass was roughly the mean of the other two.
44. Which triad consisted of halogens?
ⓐ. F, Cl, Br
ⓑ. Cl, Br, I
ⓒ. Br, I, At
ⓓ. Cl, F, I
Correct Answer: Cl, Br, I
Explanation: Chlorine (35.5), bromine (80), and iodine (127) formed a triad. The average of chlorine and iodine $(35.5+127)/2=81.25$ is close to bromine’s atomic mass (80). Their chemical properties, such as forming -1 ions and reacting with metals to form halides, also showed similarity. This confirmed Döbereiner’s observation of trends within groups.
45. Why was Döbereiner’s Triad rule not universally applicable?
ⓐ. It only worked for isotopes.
ⓑ. It could be applied to very few elements.
ⓒ. It was based on atomic number.
ⓓ. It explained variable valency.
Correct Answer: It could be applied to very few elements.
Explanation: Döbereiner’s law of triads was useful but limited. Only a small number of elements fit into triads. For example, elements like fluorine, oxygen, and nitrogen could not be placed properly. By the mid-19th century, more than 50 elements were known, but only a handful could be arranged as triads, reducing its significance.
46. What mathematical relation did Döbereiner observe in his triads?
ⓐ. Sum of all three atomic masses = constant
ⓑ. Square root of atomic masses matched
ⓒ. Mean atomic mass of the first and third ≈ second element
ⓓ. Cube root law of atomic masses
Correct Answer: Mean atomic mass of the first and third ≈ second element
Explanation: Döbereiner noticed a simple numerical pattern: if three elements were arranged in order of increasing atomic mass, the second element’s mass was approximately the arithmetic mean of the first and third. For example, $(7+39)/2=23$ for Li, Na, K. This relation was one of the earliest quantitative correlations in chemistry classification.
47. In which year did Döbereiner propose his Triad law?
ⓐ. 1789
ⓑ. 1817
ⓒ. 1869
ⓓ. 1913
Correct Answer: 1817
Explanation: Döbereiner proposed his triads in 1817, much before Mendeleev’s periodic table (1869). It was an early attempt at systematic classification. Though limited, it laid the foundation for the idea that properties of elements vary periodically with atomic mass/number.
48. Which of the following is NOT an example of a Döbereiner triad?
ⓐ. Li, Na, K
ⓑ. Ca, Sr, Ba
ⓒ. Cl, Br, I
ⓓ. C, N, O
Correct Answer: C, N, O
Explanation: Carbon, nitrogen, and oxygen do not form a triad because the atomic mass of nitrogen (14) is not the mean of carbon (12) and oxygen (16). Their chemical properties also differ significantly. Hence, not all elements could be arranged as triads, exposing the law’s limitations.
49. What was the major contribution of Döbereiner’s Triads?
ⓐ. Discovery of isotopes
ⓑ. Early indication of periodicity in properties of elements
ⓒ. Accurate determination of atomic numbers
ⓓ. Development of modern periodic law
Correct Answer: Early indication of periodicity in properties of elements
Explanation: Döbereiner’s Triads were important because they hinted at periodicity—that properties of elements are related to their atomic masses. This concept was later refined by Mendeleev (atomic mass) and Moseley (atomic number). Though imperfect, it was the first step toward periodic classification.
50. Why did Döbereiner’s Triads lose importance by the mid-19th century?
ⓐ. Only a few elements could be grouped in triads.
ⓑ. The atomic masses of many elements did not fit the rule.
ⓒ. More than 50 elements were known, and triads became insufficient.
ⓓ. All of the above.
Correct Answer: All of the above.
Explanation: Döbereiner’s system was very limited—it could apply only to 3 or 4 triads. Many elements did not fit the rule, and as more elements were discovered, the system became inadequate. Nevertheless, it demonstrated the importance of trends and relationships between elements, paving the way for more advanced classifications.
51. Who proposed the Law of Octaves in 1864?
ⓐ. Mendeleev
ⓑ. Newlands
ⓒ. Moseley
ⓓ. Dobereiner
Correct Answer: Newlands
Explanation: John Newlands, an English chemist, proposed the “Law of Octaves” in 1864. He arranged elements in order of increasing atomic mass and observed that every eighth element showed properties similar to the first, just like notes in a musical octave.
52. According to Newlands’ Law of Octaves, the properties of which elements were similar?
ⓐ. Every 5th and 10th element
ⓑ. Every 7th element
ⓒ. Every 8th element
ⓓ. Consecutive elements only
Correct Answer: Every 8th element
Explanation: Newlands observed that when elements were arranged by increasing atomic mass, the 8th element resembled the 1st in properties. For example, lithium (Li) and sodium (Na) showed similar chemical behavior, reflecting a periodic repetition in properties.
53. How many elements did Newlands arrange while proposing his Law of Octaves?
ⓐ. 33
ⓑ. 56
ⓒ. 63
ⓓ. 92
Correct Answer: 56
Explanation: At the time of Newlands’ work, 56 elements were known. He tried to fit them into his octave pattern. However, the law worked well only for lighter elements and failed for heavier ones beyond calcium.
54. Which of the following pairs best demonstrates Newlands’ Octaves?
ⓐ. Li and Na
ⓑ. Be and Mg
ⓒ. F and Cl
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Lithium and sodium (alkali metals), beryllium and magnesium (alkaline earth metals), fluorine and chlorine (halogens) all showed similar properties, confirming the “eighth element similarity” Newlands described.
55. Why was Newlands’ Law of Octaves criticized?
ⓐ. It worked only up to calcium
ⓑ. It forced dissimilar elements into the same group
ⓒ. He compared it with music, which was mocked
ⓓ. All of the above
Correct Answer: All of the above
Explanation: The law was ridiculed because Newlands compared chemistry with musical notes. It also failed beyond calcium since heavier elements didn’t follow the rule. Furthermore, to maintain the pattern, he sometimes placed dissimilar elements together, reducing its accuracy.
56. Which limitation of Newlands’ Octaves showed its inadequacy?
ⓐ. Noble gases were not discovered at the time
ⓑ. It ignored isotopes
ⓒ. It could not arrange elements beyond calcium properly
ⓓ. All of the above
Correct Answer: All of the above
Explanation: At the time, noble gases were unknown, isotopes were not considered, and elements heavier than calcium (Z > 20) did not follow the octave law. Hence, the law was incomplete and eventually discarded, though it inspired later systems.
57. Newlands’ Octaves worked well for which set of elements?
ⓐ. Lighter elements up to calcium
ⓑ. Transition metals
ⓒ. Lanthanides
ⓓ. Actinides
Correct Answer: Lighter elements up to calcium
Explanation: For the first 20 elements, Newlands’ Law of Octaves was fairly accurate, since periodicity in their properties was visible. Beyond calcium, the increasing complexity of d- and f-block elements caused the law to fail.
58. Which of the following dissimilar elements were forced into the same column by Newlands?
ⓐ. Co and Ni with halogens
ⓑ. H and He with noble gases
ⓒ. C and N with metals
ⓓ. Na and K with noble gases
Correct Answer: Co and Ni with halogens
Explanation: In his arrangement, cobalt and nickel were placed with fluorine, chlorine, and bromine, despite being metals with very different properties. This misplacement was one of the major criticisms of the law.
59. What was the significance of Newlands’ Law of Octaves despite its limitations?
ⓐ. It introduced atomic number
ⓑ. It emphasized periodic repetition of properties
ⓒ. It explained isotopes
ⓓ. It led directly to the discovery of electrons
Correct Answer: It emphasized periodic repetition of properties
Explanation: Even though it failed in many cases, Newlands’ law was the first to show that properties of elements repeat at regular intervals. This concept of periodicity became the foundation for Mendeleev’s and Moseley’s later work.
60. Why did scientists reject Newlands’ Law of Octaves initially?
ⓐ. Because it was too advanced
ⓑ. Because it was not applicable to most elements
ⓒ. Because noble gases were already known
ⓓ. Because it used atomic number instead of mass
Correct Answer: Because it was not applicable to most elements
Explanation: The law failed for elements beyond calcium and forced many dissimilar elements together. As more elements were discovered, its shortcomings became obvious. Despite being mocked, it was later recognized as an important step toward the development of the periodic law.
61. On what basis did Mendeleev arrange the elements in his periodic table?
ⓐ. Increasing atomic number
ⓑ. Increasing atomic mass
ⓒ. Increasing valency
ⓓ. Alphabetical order of names
Correct Answer: Increasing atomic mass
Explanation: Mendeleev in 1869 arranged the 63 known elements in order of increasing atomic mass. He observed that after certain intervals, the elements with similar chemical properties recurred, which led him to propose the periodic law based on atomic mass. This arrangement also allowed him to leave gaps for undiscovered elements.
62. What did Mendeleev’s Periodic Law state?
ⓐ. Properties of elements are a periodic function of their atomic numbers.
ⓑ. Properties of elements are random with respect to atomic mass.
ⓒ. Properties of elements are a periodic function of their atomic masses.
ⓓ. Properties of elements are unrelated to atomic structure.
Correct Answer: Properties of elements are a periodic function of their atomic masses.
Explanation: Mendeleev’s law was based on atomic mass since atomic number was not yet discovered. He observed that chemical properties of elements repeat periodically when arranged in increasing order of their atomic masses. This was later modified by Moseley to atomic number.
63. How many groups and periods were present in Mendeleev’s original table?
ⓐ. 8 groups and 6 periods
ⓑ. 7 groups and 7 periods
ⓒ. 10 groups and 5 periods
ⓓ. 18 groups and 7 periods
Correct Answer: 8 groups and 6 periods
Explanation: Mendeleev’s periodic table had 8 vertical groups (with subgroups A and B) and 6 horizontal periods. The groups combined elements with similar properties, while periods represented increasing atomic mass.
64. Which element’s properties did Mendeleev successfully predict before its discovery?
ⓐ. Neon
ⓑ. Germanium
ⓒ. Helium
ⓓ. Francium
Correct Answer: Germanium
Explanation: Mendeleev left gaps in his table and predicted the properties of undiscovered elements such as “eka-silicon,” which was later discovered as germanium. Its actual properties matched closely with his predictions, validating the usefulness of his table.
65. Why did Mendeleev leave gaps in his periodic table?
ⓐ. Because he did not know atomic numbers
ⓑ. To maintain the octave law
ⓒ. For elements that were undiscovered at the time
ⓓ. To separate metals from non-metals
Correct Answer: For elements that were undiscovered at the time
Explanation: Mendeleev confidently left gaps in his table, predicting that new elements would eventually be discovered to fill them. Examples include gallium (eka-aluminium), scandium (eka-boron), and germanium (eka-silicon).
66. How did Mendeleev classify hydrogen?
ⓐ. Only with alkali metals
ⓑ. Only with halogens
ⓒ. Placed in group IA but also showed similarities with halogens
ⓓ. Not included in the table
Correct Answer: Placed in group IA but also showed similarities with halogens
Explanation: Hydrogen was placed with alkali metals in group IA due to its valency of +1, but it also resembled halogens in forming diatomic molecules and covalent compounds. This dual nature made its position debatable.
67. Which unusual step did Mendeleev take to keep elements with similar properties together?
ⓐ. Ignored isotopes
ⓑ. Reversed the order of some elements despite atomic masses
ⓒ. Used atomic number
ⓓ. Grouped noble gases with halogens
Correct Answer: Reversed the order of some elements despite atomic masses
Explanation: Mendeleev placed some elements out of strict order of atomic mass (e.g., cobalt before nickel) to ensure grouping by chemical properties. This showed his insight that properties are more fundamental than atomic mass.
68. What was one of the major achievements of Mendeleev’s table?
ⓐ. Discovery of isotopes
ⓑ. Prediction of properties of unknown elements
ⓒ. Introduction of atomic number
ⓓ. Classification of noble gases
Correct Answer: Prediction of properties of unknown elements
Explanation: Mendeleev’s genius was evident when the properties he predicted for undiscovered elements (eka-aluminium, eka-boron, eka-silicon) matched closely with the properties of gallium, scandium, and germanium discovered later. This proved the validity of his classification.
69. Which group of elements was not included in Mendeleev’s original periodic table?
ⓐ. Alkali metals
ⓑ. Alkaline earth metals
ⓒ. Noble gases
ⓓ. Transition metals
Correct Answer: Noble gases
Explanation: Noble gases (He, Ne, Ar, etc.) were not discovered until the late 19th century. After their discovery, they were placed in a separate group (Group 0) without disturbing the main framework of Mendeleev’s table.
70. Why was Mendeleev’s classification widely accepted at that time?
ⓐ. It was based on atomic number
ⓑ. It gave a logical arrangement of known elements and predicted new ones
ⓒ. It ignored anomalies completely
ⓓ. It used electronic configuration
Correct Answer: It gave a logical arrangement of known elements and predicted new ones
Explanation: Mendeleev’s table provided order to 63 known elements, explained their similarities, and most importantly predicted new elements. Despite anomalies, its success in predictions made it a powerful tool for chemists and secured wide acceptance.
71. What was the greatest achievement of Mendeleev’s periodic table?
ⓐ. Discovery of isotopes
ⓑ. Successful prediction of undiscovered elements
ⓒ. Use of atomic numbers
ⓓ. Classification of noble gases
Correct Answer: Successful prediction of undiscovered elements
Explanation: Mendeleev’s genius lay in leaving gaps in his table and predicting the properties of elements like gallium (eka-aluminium), scandium (eka-boron), and germanium (eka-silicon). When these elements were discovered, their properties closely matched his predictions, proving the strength of his classification.
72. Which feature of Mendeleev’s periodic table allowed noble gases to be easily accommodated after their discovery?
ⓐ. Use of atomic numbers
ⓑ. Group 0 could be added without disturbing existing groups
ⓒ. Reversal of atomic masses
ⓓ. Ignoring isotopes
Correct Answer: Group 0 could be added without disturbing existing groups
Explanation: Noble gases were discovered later, but because of Mendeleev’s flexible structure, they were placed in a new Group 0 at the end. This was a major achievement since his table could accommodate new findings without disruption.
73. How did Mendeleev’s table help in unifying elements?
ⓐ. By showing a clear relation between atomic structure and isotopes
ⓑ. By grouping together elements with similar properties
ⓒ. By eliminating transition metals
ⓓ. By arranging all elements by atomic number
Correct Answer: By grouping together elements with similar properties
Explanation: Mendeleev grouped elements with similar chemical behavior, such as alkali metals, alkaline earth metals, and halogens. This unified understanding helped chemists study families of elements instead of each one individually.
74. Which anomaly did Mendeleev deliberately accept to keep elements with similar properties in the same group?
ⓐ. Cobalt and nickel arrangement
ⓑ. Copper and zinc misplacement
ⓒ. Potassium and argon misplacement
ⓓ. Oxygen and sulfur grouping
Correct Answer: Cobalt and nickel arrangement
Explanation: Mendeleev placed cobalt (58.9) before nickel (58.7) despite higher atomic mass, because cobalt’s properties matched better with Group 9. This showed his insight that properties were more fundamental than strict mass order.
75. Which of the following is an achievement of Mendeleev’s table?
ⓐ. Systematic study of element properties
ⓑ. Prediction of new elements
ⓒ. Accommodation of noble gases
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Mendeleev’s periodic table was remarkable for arranging elements systematically, predicting unknown elements, and being flexible enough to incorporate noble gases later. These achievements made it the foundation for modern classification.
76. Which major limitation was exposed in Mendeleev’s periodic law?
ⓐ. It failed for isotopes
ⓑ. It was based on atomic mass instead of atomic number
ⓒ. Some elements did not follow increasing order of atomic mass
ⓓ. All of the above
Correct Answer: All of the above
Explanation: The reliance on atomic mass caused anomalies. Isotopes had to be placed separately despite identical properties. Some elements like Co and Ni, Te and I did not fit perfectly into mass order. Later, Moseley corrected this by using atomic number.
77. Why was the position of hydrogen a limitation in Mendeleev’s table?
ⓐ. It was not discovered at the time
ⓑ. It could not be placed definitively in one group
ⓒ. It had too many isotopes
ⓓ. It was heavier than helium
Correct Answer: It could not be placed definitively in one group
Explanation: Hydrogen showed dual behavior—like alkali metals (forming H⁺ ions) and like halogens (forming H⁻ ions). Mendeleev placed it with alkali metals but acknowledged its similarities with halogens, leaving its position uncertain.
78. Which pair of elements was misplaced in Mendeleev’s table when arranged strictly by atomic mass?
ⓐ. Na and Mg
ⓑ. Cl and Br
ⓒ. Te and I
ⓓ. Fe and Co
Correct Answer: Te and I
Explanation: Tellurium (127.6) was placed before iodine (126.9) because iodine’s properties matched Group 17 (halogens). This mass anomaly was unexplained until Moseley’s atomic number concept resolved it.
79. Why could isotopes not be accommodated properly in Mendeleev’s table?
ⓐ. They had different atomic numbers
ⓑ. They had different chemical properties
ⓒ. They had identical chemical properties but different masses
ⓓ. They did not exist during Mendeleev’s time
Correct Answer: They had identical chemical properties but different masses
Explanation: Isotopes like Cl-35 and Cl-37 should occupy different positions if classified by mass, but they had identical chemical behavior. This limitation highlighted the weakness of atomic mass as a basis for classification.
80. Why did the discovery of noble gases create a problem for Mendeleev’s table initially?
ⓐ. They were metals but placed with halogens
ⓑ. They had zero valency and did not fit any existing group
ⓒ. They had fractional atomic masses
ⓓ. They were unstable and short-lived
Correct Answer: They had zero valency and did not fit any existing group
Explanation: Noble gases were unknown when Mendeleev proposed his table. Their discovery posed a challenge because they did not react with other elements. Later, they were accommodated into a new Group 0, but initially, this was a limitation.
81. Why was Mendeleev’s law eventually modified?
ⓐ. Atomic mass was not a fundamental property
ⓑ. Atomic number gave a more precise arrangement
ⓒ. X-ray experiments proved nuclear charge determined properties
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Moseley’s X-ray studies in 1913 showed that atomic number (nuclear charge), not atomic mass, determined element properties. This corrected anomalies and gave rise to the Modern Periodic Law, refining Mendeleev’s foundation.
82. Who gave the Modern Periodic Law in 1913?
ⓐ. Mendeleev
ⓑ. John Newlands
ⓒ. Henry Moseley
ⓓ. J.J. Thomson
Correct Answer: Henry Moseley
Explanation: Moseley’s X-ray diffraction experiments in 1913 proved that the atomic number (proton number) is the fundamental property of elements. He formulated the Modern Periodic Law: “The physical and chemical properties of elements are a periodic function of their atomic numbers.” This replaced Mendeleev’s atomic mass–based law.
83. What does the Modern Periodic Law state?
ⓐ. Properties of elements are a periodic function of their atomic numbers.
ⓑ. Properties of elements are a periodic function of their atomic masses.
ⓒ. Properties of elements are random and irregular.
ⓓ. Properties of elements are independent of atomic structure.
Correct Answer: Properties of elements are a periodic function of their atomic numbers.
Explanation: Modern Periodic Law emphasizes atomic number as the basis of classification. Since atomic number defines nuclear charge and electronic configuration, it explains periodic repetition of properties far more accurately than atomic mass.
84. How did Moseley experimentally determine atomic number?
ⓐ. By chemical reactions of elements
ⓑ. By X-ray emission spectra
ⓒ. By cathode ray experiments
ⓓ. By studying isotopes
Correct Answer: By X-ray emission spectra
Explanation: Moseley bombarded elements with high-energy electrons and observed the X-ray frequencies emitted. He found these frequencies were proportional to atomic number ($\nu \propto (Z-1)^2$), thus confirming atomic number is a measurable physical property that determines periodicity.
85. Which anomaly of Mendeleev’s table was corrected by the Modern Periodic Law?
ⓐ. Position of noble gases
ⓑ. Misplacement of isotopes
ⓒ. Inversion of iodine and tellurium order
ⓓ. All of the above
Correct Answer: All of the above
Explanation: By using atomic number instead of mass, modern periodic law resolved key anomalies: isotopes (same Z placed together), Te and I order explained, and noble gases fitted naturally as Group 18 due to their full outer shells.
86. What was the major advantage (pro) of the Modern Periodic Law?
ⓐ. It was based on atomic mass
ⓑ. It explained isotopes and periodicity accurately
ⓒ. It ignored noble gases
ⓓ. It excluded transition elements
Correct Answer: It explained isotopes and periodicity accurately
Explanation: The Modern Periodic Law, based on atomic number, eliminated earlier flaws. Isotopes (same Z) were placed together, and periodicity was linked to electronic configuration. This made classification more consistent and logical.
87. Which of the following is a disadvantage (con) of the Modern Periodic Law?
ⓐ. Hydrogen’s position is still uncertain
ⓑ. Theories on superheavy elements are incomplete
ⓒ. Inner transition elements (f-block) had to be placed separately
ⓓ. All of the above
Correct Answer: All of the above
Explanation: Despite its strength, Modern Periodic Law does not perfectly solve all issues. Hydrogen can be placed with Group 1 or Group 17. Lanthanides and actinides are shown separately to keep the table compact. Also, superheavy element behavior is still under study.
88. When was the Modern Periodic Table adopted in its long-form version?
ⓐ. 1789
ⓑ. 1869
ⓒ. Early 20th century (after Moseley’s work)
ⓓ. 2000
Correct Answer: Early 20th century (after Moseley’s work)
Explanation: After Moseley’s discovery in 1913, chemists gradually adopted the atomic-number–based classification. By the 1920s, the long-form periodic table was widely used, aligning periodicity with electronic configuration.
89. Why is atomic number considered more fundamental than atomic mass?
ⓐ. Because it varies irregularly
ⓑ. Because it determines nuclear charge and electron configuration
ⓒ. Because it is easier to measure than mass
ⓓ. Because it changes with isotopes
Correct Answer: Because it determines nuclear charge and electron configuration
Explanation: Atomic number defines the number of protons in the nucleus. Since chemical properties depend on valence electrons, which are determined by nuclear charge, atomic number is the true basis for classification. Atomic mass can vary (isotopes), but atomic number is fixed.
90. Which statement best summarizes the significance of the Modern Periodic Law?
ⓐ. It is outdated and no longer useful.
ⓑ. It unified chemical and physical properties under atomic number.
ⓒ. It grouped elements randomly.
ⓓ. It ignored electron configuration.
Correct Answer: It unified chemical and physical properties under atomic number.
Explanation: The Modern Periodic Law provided a strong scientific foundation by linking element properties directly to atomic number and electronic configuration. It not only resolved past anomalies but also allowed prediction of properties of superheavy elements, making it the most accurate system till date.
91. How many periods are present in the long form of the modern periodic table?
ⓐ. 6
ⓑ. 7
ⓒ. 8
ⓓ. 9
Correct Answer: 7
Explanation: The modern long-form periodic table has 7 horizontal rows called periods. Each period corresponds to the filling of successive electron shells (n = 1 to 7). For example, Period 1 contains H and He (n = 1), while Period 7 involves filling of 7s, 5f, 6d, and 7p orbitals.
92. How many groups are present in the modern periodic table?
ⓐ. 7
ⓑ. 8
ⓒ. 18
ⓓ. 32
Correct Answer: 18
Explanation: The vertical columns of the periodic table are called groups. There are 18 groups, numbered from 1 to 18. Elements in a group share similar valence shell electronic configurations, leading to similar chemical properties. For example, Group 1 elements are alkali metals.
93. Which period in the periodic table is the longest?
ⓐ. 1st period
ⓑ. 2nd period
ⓒ. 6th period
ⓓ. 7th period
Correct Answer: 6th period
Explanation: The 6th period contains 32 elements, including the 14 lanthanides. It involves filling of 6s, 4f, 5d, and 6p orbitals. This makes it the longest period in the periodic table.
94. How many elements are there in the first period?
ⓐ. 2
ⓑ. 8
ⓒ. 18
ⓓ. 32
Correct Answer: 2
Explanation: The first period contains only hydrogen and helium. This is because only 1s orbital is available for filling (maximum 2 electrons). It is the shortest period in the periodic table.
95. Which period contains the lanthanides?
ⓐ. 4th period
ⓑ. 5th period
ⓒ. 6th period
ⓓ. 7th period
Correct Answer: 6th period
Explanation: The 6th period contains the lanthanides (Z = 57 to 71). They belong to the f-block and are usually placed separately at the bottom of the periodic table for compactness.
96. Which group is known as the noble gases?
ⓐ. Group 1
ⓑ. Group 2
ⓒ. Group 17
ⓓ. Group 18
Correct Answer: Group 18
Explanation: Elements of Group 18 (He, Ne, Ar, Kr, Xe, Rn, Og) are noble gases. They have completely filled valence shells, which makes them chemically inert under normal conditions.
97. Which group is called the alkali metals?
ⓐ. Group 1
ⓑ. Group 2
ⓒ. Group 13
ⓓ. Group 17
Correct Answer: Group 1
Explanation: Group 1 elements (Li, Na, K, Rb, Cs, Fr) are alkali metals. They have one valence electron (ns¹), form strongly basic hydroxides, and are highly reactive, especially with water.
98. Which group is known as the halogens?
ⓐ. Group 14
ⓑ. Group 15
ⓒ. Group 16
ⓓ. Group 17
Correct Answer: Group 17
Explanation: Group 17 elements (F, Cl, Br, I, At, Ts) are called halogens, meaning “salt-formers.” They have seven valence electrons (ns²np⁵), form -1 anions, and combine readily with metals to form halides.
99. Why are lanthanides and actinides placed separately at the bottom of the periodic table?
ⓐ. To highlight their radioactivity
ⓑ. To make the table compact and organized
ⓒ. Because they do not follow periodic law
ⓓ. Because they are not metals
Correct Answer: To make the table compact and organized
Explanation: f-block elements (lanthanides and actinides) are placed separately below the main body of the periodic table. If inserted in their proper positions, the table would be too wide. Separating them keeps the table manageable while preserving order.
100. Which of the following is true about groups in the periodic table?
ⓐ. Elements in the same group have different valence electron configurations.
ⓑ. Elements in the same group have identical valence shell electronic configurations.
ⓒ. Elements in the same group are always metals.
ⓓ. Elements in the same group have random properties.
Correct Answer: Elements in the same group have identical valence shell electronic configurations.
Explanation: Groups represent vertical columns where elements have the same number of valence electrons. For example, Group 2 elements (Be, Mg, Ca, Sr, Ba, Ra) all have ns² configuration. This similarity leads to similar chemical properties within a group.
FAQs on Classification of Elements and Periodicity in Properties ▼
▸ What are Classification of Elements and Periodicity MCQs?
These are multiple-choice questions from Chapter 3 of NCERT Class 11 Chemistry. They cover classification of elements, periodic law, modern periodic table, and periodic trends in properties.
▸ How many MCQs are available in this chapter?
There are a total of 350 MCQs, divided into 4 parts – three sets of 100 questions each and one set of 50 questions.
▸ Are these Chemistry MCQs useful for NCERT and CBSE board exams?
Yes, these MCQs are directly based on the NCERT/CBSE Class 11 Chemistry syllabus and are highly useful for board exams, providing strong practice and conceptual clarity.
▸ Are these MCQs important for competitive exams like JEE and NEET?
Yes, this chapter is very important for JEE, NEET, and other entrance exams. Periodic trends such as ionization enthalpy, electron gain enthalpy, and electronegativity are frequently asked in competitive tests.
▸ Do these MCQs include answers and explanations?
Yes, every MCQ comes with the correct answer and explanations wherever needed. This helps students understand the reasoning behind the concepts and avoid confusion in exams.
▸ Who should practice these Chemistry MCQs?
These MCQs are ideal for Class 11 students, state board learners, and aspirants of JEE, NEET, UPSC, SSC, and other competitive exams where Chemistry plays an important role.
▸ Can I practice these Chemistry MCQs online for free?
Yes, all Classification of Elements and Periodicity MCQs are available online for free. They can be practiced anytime on mobile, tablet, or desktop.
▸ Are these MCQs helpful for quick revision?
Yes, practicing these MCQs regularly helps in quick revision, strengthens memory recall, and improves exam performance by enhancing accuracy and speed.
▸ Do these MCQs cover both basics and advanced concepts?
Yes, they cover basic topics like Mendeleev’s periodic table and modern periodic law, as well as advanced topics like periodic trends, electronegativity, and diagonal relationships.
▸ Which subtopics are included in these MCQs?
The MCQs include subtopics such as modern periodic law, classification of elements, ionization enthalpy, electron gain enthalpy, electronegativity, periodic variation, valency, and diagonal relationships.
▸ Why are the 350 MCQs divided into 4 parts?
They are divided into 4 sets to make practice easier and more structured, helping students focus step by step instead of being overwhelmed by all questions at once.
▸ Can teachers and coaching institutes use these Chemistry MCQs?
Yes, teachers and coaching centers can use these MCQs as ready-made assignments, quizzes, and practice resources for board and competitive exam preparation.
▸ Are these MCQs mobile-friendly?
Yes, the Classification of Elements and Periodicity MCQs pages are optimized for smartphones and tablets so students can study anytime, anywhere.
▸ Can I download or save these MCQs for offline study?
Yes, you can download these Chemistry MCQs in PDF format for offline study. Please visit our website shop.gkaim.com
Welcome to Class 11 Chemistry MCQs – Chapter 3: Classification of Elements and Periodicity in Properties (Part 1). This chapter in the NCERT/CBSE Class 11 Chemistry syllabus is among the most scoring and concept-building topics, as it explains how elements are systematically arranged in the Periodic Table and how their properties vary in a predictable manner. The chapter begins with the historical development of the periodic classification—from Dobereiner’s Triads, Newlands’ Law of Octaves, and Mendeleev’s Periodic Table to the formulation of the Modern Periodic Law and the adoption of the long form of the periodic table. Understanding these concepts is crucial for board exams, JEE Main, NEET, state entrance tests, and even international competitive exams.
The periodic table is the backbone of Chemistry—mastery of this chapter makes later topics like chemical bonding, coordination chemistry, and inorganic reactions much easier.
Navigation & pages: The full set includes 350 MCQs arranged into 4 parts (100 + 100 + 100 + 50). Part 1 provides the first 100 MCQs, presented in 10 pages with 10 questions per page. Use the page numbers above to browse questions, and the Part buttons above to continue with the next sets.
What you will learn & practice
- Early attempts of classification: Dobereiner’s Triads, Newlands’ Octaves
- Mendeleev’s Periodic Table — merits, limitations, and predictions
- Modern Periodic Law and long form of periodic table
- Groups, periods, blocks (s, p, d, f), and element positions
- Periodic trends:
- Variation of atomic radius and ionic radius
- Ionization enthalpy trends
- Electron gain enthalpy (1st & 2nd) and factors affecting it
- Electronegativity (Pauling scale, Mulliken’s definition)
- Valency and relation with group number
- Variable valency with examples
- Diagonal relationship (Li–Mg, Be–Al, B–Si)
- Different chemistry of lighter vs heavier congeners
- Factors: small size, high electronegativity, absence of d-orbitals
- Applications of periodic trends in predicting chemical behaviour
- MCQs based on reasoning + numerical problems (atomic size, IE difference, etc.)
How this practice works
- Click an option to check instantly: green dot = correct, red icon = incorrect. The Correct Answer with explanation is revealed.
- Use the 👁️ Eye icon to directly view the solution + explanation.
- Use the 📝 Notebook icon as a temporary scratchpad (notes are not saved).
- Use the ⚠️ Alert icon to report errors or issues instantly.
- Use the 💬 Message icon to comment, ask doubts, or join discussions.
Real value: These MCQs are prepared strictly on the NCERT/CBSE syllabus, shaped by previous-year question trends, and explained with concise, exam-oriented solutions. Ideal for one-mark board exam questions, concept strengthening, and competitive test preparation.
The full chapter includes 350 solved MCQs in 4 systematic parts. This page (Part 1) contains the first 100 MCQs with answers and explanations. Explore more with: Class 11 Chemistry – Chapter Index, Class 11 – Subject Index, All Classes – MCQ Library.
- 👉 Total MCQs in this chapter: 350 (100 + 100 + 100 + 50)
- 👉 This page: First 100 MCQs with answers & explanations (in 10 pages)
- 👉 Best for: Boards • JEE/NEET • periodic table practice • concept revision • Chemistry quizzes
- 👉 Next: Use the Part buttons and page numbers above to continue