NIOS Class 10 Science and Technology Chapter 6 : PERIODIC CLASSIFICATION OF ELEMENTS – Chapter-wise Important Questions and Answers
NIOS Class 10 Science and Technology Chapter 6 : PERIODIC CLASSIFICATION OF ELEMENTS | MCQs, Short & Long Answer Questions | 6 : PERIODIC CLASSIFICATION OF ELEMENTS
Chapter 6 : PERIODIC CLASSIFICATION OF ELEMENTS
INTEXT QUESTIONS 6.1
1. Elements A, B and C constitute a Dobereiner’s triad. The atomic mass of A is 20 and that of C is 40. Predict the atomic mass of B.
Answer: Here, A = 20 and C = 40
Atomic mass of B =20 + 402 =602 = 30
Therefore, the atomic mass of B is 30.
2. Which property of atoms was used by Mendeleev to classify the elements?
Answer: Mendeleev classified the elements mainly on the basis of their atomic mass.
3. In Mendeleev’s periodic classification, whether chemically similar elements are placed in a group or in a period?
Answer: In Mendeleev’s periodic table, chemically similar elements are placed in a group.
4. Mendeleev’s periodic table had some blank spaces. What did they signify?
Answer: The blank spaces in Mendeleev’s periodic table showed the positions of elements that were not yet discovered at that time.
5. Explain any three defects of Mendeleev’s periodic table.
Answer: Three defects of Mendeleev’s periodic table are:
(i) Position of hydrogen: Hydrogen showed properties similar to both alkali metals and halogens, so its exact position in the table was not fixed properly.
(ii) Position of isotopes: Since isotopes have different atomic masses but same chemical properties, Mendeleev’s arrangement based on atomic mass could not place them correctly.
(iii) Anomalous pairs of elements In some cases, elements with higher atomic mass were placed before lower atomic mass elements (like cobalt and nickel), which disturbed the proper order.
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