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Periodic Classification of Elements — Science STD 10 — Question

CBSE BoardEnglish MediumSTD 10SciencePeriodic Classification of Elements5 Marks
Question
  1. Which two criteria did Mendeleev use to classify the elements in his periodic table?
  2. State Mendeleev’s periodic law.
  3. Why could no fixed position be given to hydrogen in Mendeleev’s periodic table?
  4. How and why does the atomic size vary as you go:
  1. From left to right along a period?
  2. Down a group?
✓

Answer

  1. The criteria used by Mendeleev in creating his periodic table:
  1. He arranged the elements on the basis of their increasing atomic masses.
  2. He put elements of similar properties in a group.
  1. He gave a law known as periodic law. The law states that the physical and chemical properties of elements are periodic function of their atomic weights.
  2. Hydrogen resembles like both the alkali metals and the halogens. Hence, it was placed in I A group VI B group and could not be given a fixed position in Mendeleev’s Periodic Table.
  1.  
  1. When we move from left to right in periodic table no. of shells remain same but the no. of electron increases due to which the size of an atom decreases.
  2. When we move down a group the no. of shells goes on increases and hence the size of atom also increases.

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