Class 10: Periodic Classification of Elements

NCERT Exemplar Problems

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Very Short Answer Type Questions:

  1. The earliest attempt at classification of elements made how many groups of elements? Name those groups.
  2. Dobereiner could make how many triads?
  3. How many elements were known at the time of Newlands?
  4. Newlands Law of Octaves could be applicable to which type of elements?

Fill in the blanks:

  1. Dobereiner could arrange just …………elements in triads.
  2. ……………was the last element in Newlands’ table.
  3. …………….was the first element in Newlands’ table.
  4. Calcium is at ………….position in Newlands’ table.

Write True/False for the following:

  1. Dobereiner’s triads could be applied to a large number of elements.
  2. Newlands assumed that new elements would not be discovered in future.
  3. Newlands belonged to England.
  4. Newlands Law of Octaves got wide acceptance among scientists.
  5. Dobereiner arranged elements in increasing order of atomic mass.

Short Answer Type Questions:

  1. Show how do lithium, sodium and potassium make a triad; as per Doebreiner.
  2. How many elements were known during the time of Newlands? How did arrange the elements?

Long Answer Type Questions:

  1. What were the limitations of Newlands Law of Octaves?

Multiple Choice Questions

  1. How many elements could fit in Dobereinr’s triads?
  • a. 3
  • b. 6
  • c. 9
  • d. 12
  1. What is the average of atomic masses of lithium and potassium?
  • a. 9
  • b. 0
  • c. 0
  • d. 2
  1. Newlands’ Law of Octaves could be applied up to which of the following elements?
  • a. Iron
  • b. Chlorine
  • c. Sodium
  • d. Calcium
  1. Newlands Law was similar to which of the following?
  • a. Colours of rainbow
  • b. Notes of music
  • c. Planets in solar system
  • d. Days of week

Periodic Classification of Elements

Brainstorming Session

  1. Why was the classification of elements into metals and non-metals, not enough?

Answer 5.1

Very Short Answer Type Questions:

  1. Answer: The earliest attempt at classification of elements made two groups, viz. metals and nonmetals.
  2. Answer: Three
  3. Answer: 56
  4. Answer: Light elements

Fill in the blanks:

  1. Answer: nine
  2. Answer: Thorium
  3. Answer: Hydrogen
  4. Answer: Nineteenth

Write True/False for the following:

Answer: 1→ F, 2→ T, 3 → T, 4 → F, 5 → T

Short Answer Type Questions:

  1. Answer: an Atomic mass of lithium = 6.9

Atomic mass of potassium = 39.0

Here; the average of atomic masses of lithium and potassium is 23 which is roughly equal to that of sodium.

  1. Answer: At the time of Newlands, 56 elements were known. Newlands arranged those elements in increasing order of atomic mass.

Long Answer Type Questions:

  1. Answer: Limitations of Newlands’ Law of Octaves
  • Newlands’ Law of Octaves was applicable till calcium only. After that, the elements did not obey the law of octaves.
  • At that time, Newlands assumed that only 56 elements existed in nature and there would be no new discoveries. But when new elements were discovered, their properties did not fit this law.
  • In order to fit elements in his table, Newlands adjusted two elements in the same slot; and there are various examples of this. While doing so, he put some unlike elements in the same slot. For example; cobalt and nickel are in the same slot. Moreover, nickel and cobalt are in the same group as fluorine and chlorine. We know that properties of fluorine and chlorine are entirely different than properties of nickel and cobalt. It can also be observed that iron is put in a separate group and far from nickel and cobalt; but iron shows similar properties as nickel. Iron, cobalt and nickel are metals; while fluorine and chlorine are nonmetals.
  • It can be said that Newlands’ Law of Octaves could be applicable to lighter elements only.

Multiple Choice Questions

  1. Answer: (c) 9
  2. Answer: (b) 23.0
  3. Answer: (d) Calcium
  4. Answer: (b) Notes of music

Periodic Classification of Elements

Brainstorming Session

  1. Answer: While all metals show some similarities in chemical properties, they also show many differences. Same holds true for non-metals as well. Hence, it was not possible to study the chemical properties of elements in proper perspective by grouping them in two categories only.

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Click Exercises For Mendeleev’s Periodic Table

Chemical Reactions and Equations:

Types of Chemical Reaction:

Acids, Bases and Salts:

Common Properties of Acid and Base:

Metals and Non-metals:

Carbon and its Compounds:

Periodic Classification of Elements:

Life processes:

Control and co-ordination in animals and plants:

Reproduction:

Heredity and evolution: 

Conservation of natural resources:

How do Organism Reproduce

Electricity:

Magnetic effects of current:

Sources of energy:

Light

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