NCERT Class X Science Class: Chapter – 5. Periodic Classification of Elements – Part-10 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 46:

  1. In this ladder (Figure) symbols of elements are jumbled up. Rearrange these symbols of elements in the increasing order of their atomic number in the Periodic Table.
  2. Arrange them in the order of their group also.
Imagethe Ladder of Elements



The symbols of elements arranged in increasing order of their atomic numbers are as shown below:

Imagesymbols of Elements Arranged in Increasing Image Number …


The symbols of elements arranged in increasing order of their group numbers are as follows:

Image Symbols of Elements Image Order of Their Group Numbers

Question 47:

Mendeleev predicted the existence of certain elements not known at that time and named two of them as .

  1. Name the elements which have taken the place of these elements
  2. Mention the group and the period of these elements in the Modern Periodic Table.
  3. Classify these elements as metals, non-metals or metalloids
  4. How many valence electrons are present in each one of them?


  1. Germanium () and Gallium ()
  2. Group 14; Period 4 and Group 13; Period 4
  3. Ge — Metalloid; Ga — Metal
  4. Ga — 3 Ge — 4

Question 48:

  1. Electropositive nature of the element (s) increases down the group and decreases across the period
  2. Electronegativity of the element decreases down the group and increases across the period
  3. Atomic size increases down the group and decreases across a period (left to right)
  4. Metallic character increases down the group and decreases across a period.

On the basis of the above trends of the Periodic Table, answer the following about the elements with atomic numbers 3 to 9.

  1. Name the most electropositive element among them
  2. Name the most electronegative element
  3. Name the element with smallest atomic size
  4. Name the element which is a metalloid
  5. Name the element which shows maximum valency.


  1. Lithium
  2. Fluorine
  3. Fluorine
  4. Boron
  5. Carbon