Periodic Classification of Elements — Important Questions
46 questions
With answersCBSE format
SUMMARY: This chapter discusses the development and significance of the periodic table, the classification of elements, and the trends observed in the periodic table. KEY TOPICS: Dobereiner's Triads, Newlands' Law of Octaves, Mendeleev's Periodic Table, Modern Periodic Table, periodic trends, atomic size, metallic and non-metallic properties, valency, periodicity.
What is the general trend in atomic size as you move down a group in the periodic table?
AAtomic size decreases
BAtomic size increases
CAtomic size remains the same
DAtomic size fluctuates
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Correct answer: Option 2 — Atomic size increases
Q71 Mark
Which of the following elements is likely to have the highest metallic character?
AFluorine
BAluminum
CSodium
DChlorine
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Correct answer: Option 3 — Sodium
Q81 Mark
The valency of an element is determined by:
AThe number of protons
BThe number of electrons in the outermost shell
CThe total number of neutrons
DThe atomic mass of the element
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Correct answer: Option 2 — The number of electrons in the outermost shell
Q91 Mark
Which of the following correctly describes a property of non-metals?
AGood conductors of heat
BHigh melting points
CBrittle in solid state
DMalleable and ductile
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Correct answer: Option 3 — Brittle in solid state
Q101 Mark
Which of the following pairs of elements belong to the same group in the periodic table?
ASodium and Potassium
BBoron and Silicon
COxygen and Sulfur
DCalcium and Magnesium
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Correct answer: Option 1 — Sodium and Potassium
Q111 Mark
What is the primary limitation of Mendeleev's periodic table?
AIt did not include noble gases
BIt was not based on atomic mass
CIt could not predict the properties of undiscovered elements
DIt arranged elements randomly
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Correct answer: Option 3 — It could not predict the properties of undiscovered elements
Q121 Mark
The periodic law states that the properties of elements are a periodic function of their:
AAtomic mass
BAtomic number
CElectron affinity
DIonization energy
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Correct answer: Option 2 — Atomic number
Q131 Mark
Which of the following elements has the highest electronegativity?
AFluorine
BOxygen
CNitrogen
DChlorine
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Correct answer: Option 1 — Fluorine
Q141 Mark
As you move from top to bottom in a group, the ionization energy generally:
AIncreases
BDecreases
CRemains constant
DFluctuates
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Correct answer: Option 2 — Decreases
Short Answer Questions10 questions
Q153 Marks
What is Dobereiner's Triads and how does it contribute to the classification of elements?
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Dobereiner's Triads is a classification system proposed by Johann Wolfgang Döbereiner in the early 19th century, where he grouped elements into sets of three based on similar properties. The atomic mass of the middle element in each triad was approximately the average of the atomic masses of the other two, highlighting a relationship between elemental properties and atomic mass.
Q163 Marks
Explain Newlands' Law of Octaves and its significance in the periodic classification of elements.
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Newlands' Law of Octaves, proposed by John Newlands in 1865, states that when elements are arranged in order of increasing atomic mass, every eighth element exhibits similar properties, akin to musical octaves. This was significant as it was one of the first attempts to organize elements systematically, although it had limitations with heavier elements.
Q173 Marks
Describe Mendeleev's Periodic Table and its unique features.
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Mendeleev's Periodic Table, created by Dmitri Mendeleev in 1869, arranged elements by increasing atomic mass and grouped them by similar chemical properties. A unique feature was that Mendeleev left gaps for undiscovered elements and predicted their properties, which later were confirmed with the discovery of elements like gallium and germanium.
Q183 Marks
What are the main differences between Mendeleev's Periodic Table and the Modern Periodic Table?
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The main differences include that Mendeleev's table was based on atomic mass, while the Modern Periodic Table is organized by atomic number. Additionally, the Modern Periodic Table accounts for isotopes and provides a more accurate representation of element properties and periodic trends.
Q193 Marks
Define atomic size and explain how it varies across the periodic table.
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Atomic size refers to the distance from the nucleus to the outermost shell of an electron. It generally decreases across a period from left to right due to increased nuclear charge, which pulls electrons closer, and increases down a group due to the addition of electron shells.
Q203 Marks
What is the trend in metallic properties across a period and down a group in the periodic table?
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Metallic properties tend to decrease across a period from left to right as elements become more non-metallic in character. Conversely, metallic properties increase down a group due to the increase in atomic size and the shielding effect, making it easier for atoms to lose electrons.
Q213 Marks
Explain the concept of periodicity in the context of the periodic table.
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Periodicity refers to the recurring trends that are observed in the properties of elements when arranged by increasing atomic number. These trends include variations in atomic size, ionization energy, electronegativity, and metallic/non-metallic character, which repeat at regular intervals as one moves across periods and down groups.
Q223 Marks
What is valency and how is it determined for an element?
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Valency is the measure of an element's ability to combine with other elements, determined by the number of electrons in the outermost shell. It can be calculated based on the number of electrons an atom needs to lose, gain, or share to achieve a stable electronic configuration, typically resembling that of noble gases.
Q233 Marks
How does the atomic size change as you move down a group in the periodic table?
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As you move down a group in the periodic table, atomic size increases due to the addition of extra electron shells. This increase in distance between the nucleus and the outermost electrons outweighs the effect of increased nuclear charge, resulting in larger atomic radii.
Q243 Marks
What is the significance of the periodic trends observed in the periodic table?
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Periodic trends are significant as they provide insights into the chemical behavior and reactivity of elements. Understanding these trends helps predict how elements will interact in chemical reactions, their bonding characteristics, and their physical properties, facilitating the study of chemistry.
Long Answer Questions6 questions
Q256 Marks
Explain Dobereiner's Triads and provide an example of a triad. How did this concept contribute to the development of the periodic table?
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Dobereiner's Triads are groups of three elements that exhibit similar chemical properties, where the atomic mass of the middle element is approximately the average of the other two. For example, the elements lithium (Li), sodium (Na), and potassium (K) form a triad. This concept contributed to the development of the periodic table by suggesting that elements could be grouped based on their properties, laying the groundwork for later classification systems.
Q266 Marks
Describe Newlands' Law of Octaves and its significance in the periodic classification of elements. What were its limitations?
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Newlands' Law of Octaves states that when elements are arranged in order of increasing atomic mass, every eighth element exhibits similar properties, akin to musical octaves. This was significant as it was one of the first attempts to organize elements systematically. However, its limitations included the fact that it only worked for the first 16 elements and failed to accommodate transition metals, leading to inconsistencies in the classification.
Q276 Marks
Discuss Mendeleev's Periodic Table and how it differed from previous attempts at classification. What was its impact on the scientific community?
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Mendeleev's Periodic Table arranged elements by increasing atomic mass and grouped them based on similar chemical properties. Unlike previous classifications, Mendeleev left gaps for undiscovered elements and predicted their properties, which was revolutionary. His work had a profound impact on the scientific community, as it provided a framework for understanding elemental relationships and prompted further research into atomic structure.
Q286 Marks
What is the Modern Periodic Table, and how does it differ from Mendeleev's Periodic Table? Discuss the significance of atomic number in this context.
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The Modern Periodic Table is organized by increasing atomic number rather than atomic mass, which resolves inconsistencies found in Mendeleev's table. This change is significant because it reflects the actual structure of atoms and their properties more accurately. The use of atomic number also allows for a clearer understanding of periodic trends, such as electronegativity and ionization energy, enhancing the predictive power of the table.
Q296 Marks
Explain the concept of periodicity and how it relates to the properties of elements in the periodic table. Provide examples of periodic trends.
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Periodicity refers to the recurring trends that are observed in the properties of elements as one moves across or down the periodic table. These trends include atomic size, ionization energy, electronegativity, and metallic/non-metallic character. For example, atomic size decreases across a period due to increased nuclear charge, while it increases down a group due to additional electron shells. Such trends help in predicting the behavior of elements in chemical reactions.
Q306 Marks
Describe the trend in atomic size across a period and down a group in the periodic table. What factors influence these trends?
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As one moves across a period from left to right, atomic size decreases due to the increasing positive charge of the nucleus, which pulls the electrons closer. Conversely, as one moves down a group, atomic size increases because additional electron shells are added, which outweighs the increase in nuclear charge. Factors influencing these trends include effective nuclear charge and electron shielding effects.
Assertion–Reason Questions8 questions
Q311 Mark
Assertion (A): Dobereiner's Triads were based on the atomic masses of elements.
Reason (R): The elements in a triad showed similar chemical properties and their atomic masses followed a specific pattern.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q321 Mark
Assertion (A): Newlands' Law of Octaves applies to all known elements.
Reason (R): It states that every eighth element has similar properties, similar to musical notes.
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Correct answer: Option 3 —
A is true, but R is false.
Q331 Mark
Assertion (A): Mendeleev's Periodic Table was arranged in order of increasing atomic number.
Reason (R): Mendeleev arranged elements based on their atomic masses and properties, not atomic number.
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Correct answer: Option 3 —
A is true, but R is false.
Q341 Mark
Assertion (A): The Modern Periodic Table is based on the periodic law that states properties of elements are a periodic function of their atomic numbers.
Reason (R): This allows for a more accurate classification of elements compared to earlier tables.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q351 Mark
Assertion (A): Atomic size increases down a group in the periodic table.
Reason (R): This is due to the addition of electron shells as you move down a group.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q361 Mark
Assertion (A): Metals generally have higher electronegativity compared to non-metals.
Reason (R): Electronegativity is the tendency of an atom to attract electrons, which is higher in non-metals.
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Correct answer: Option 4 —
A is false, but R is true.
Q371 Mark
Assertion (A): Valency is determined by the number of electrons in the outermost shell of an atom.
Reason (R): This is true as valency indicates the combining capacity of an element based on its outer electrons.
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Correct answer: Option 1 —
Both A and R are true, and R is the correct explanation of A.
Q381 Mark
Assertion (A): The periodic trends for metallic properties increase from left to right across a period.
Reason (R): This is false as metallic properties decrease from left to right across a period.
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Correct answer: Option 4 —
A is false, but R is true.
Statement-Based Questions8 questions
Q391 Mark
Statement 1: Dobereiner's Triads suggest that the properties of elements can be grouped in sets of three, where the middle element has an atomic mass approximately equal to the average of the other two.
Statement 2: Newlands' Law of Octaves states that every eighth element has similar properties when arranged by increasing atomic mass.
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Correct answer: Option 1 —
Both statements are true.
Q401 Mark
Statement 1: Mendeleev's Periodic Table arranged elements based solely on their atomic number.
Statement 2: The Modern Periodic Table is arranged based on atomic number and reflects periodic trends in properties.
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Correct answer: Option 3 —
Only Statement 2 is true.
Q411 Mark
Statement 1: As you move from left to right across a period, the atomic size generally increases.
Statement 2: Non-metals tend to have higher electronegativities compared to metals in the same period.
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Correct answer: Option 2 —
Only Statement 1 is true.
Q421 Mark
Statement 1: The periodicity of elements refers to the recurring trends in their properties when they are arranged in the periodic table.
Statement 2: Valency of an element is determined by the number of protons in its nucleus.
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Correct answer: Option 1 —
Both statements are true.
Q431 Mark
Statement 1: In the Modern Periodic Table, elements are grouped into periods and groups based on their similar properties.
Statement 2: Atomic size decreases down a group due to increased shielding effect.
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Correct answer: Option 2 —
Only Statement 1 is true.
Q441 Mark
Statement 1: Newlands' Law of Octaves was applicable only up to calcium in the periodic table.
Statement 2: Mendeleev's table successfully predicted the existence of undiscovered elements based on gaps in his table.
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Correct answer: Option 1 —
Both statements are true.
Q451 Mark
Statement 1: Metals generally have higher melting points than non-metals.
Statement 2: The atomic size increases down a group due to the addition of electron shells.
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Correct answer: Option 1 —
Both statements are true.
Q461 Mark
Statement 1: The periodic table is a tool that helps in predicting the properties of elements based on their position.
Statement 2: Elements in the same group have the same number of valence electrons, which determines their chemical behavior.
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Correct answer: Option 1 —
Both statements are true.
