# Important Questions for Class 11 Chapter 3 - Classification of Elements and Periodicity in Properties

Important questions based on NCERT syllabus for Chapter 3 - Classification of Elements and Periodicity in Properties:

Question-1: What is the basic theme of organisation in the periodic table?

Solution: The basic theme of organisation of elements in the periodic table is to simplify and systematize the study of the properties of all the elements and millions of their compounds. This has made the study simple because the properties of elements are now studied in form of groups rather than individually.

Question-2: On the basis of quantum numbers, justify that the sixth period of the periodic table should have 32 elements.

Solution: The sixth period corresponds to sixth shell. The orbitals present in this shell are 6s, 4f, 5p, and 6d. The maximum number of electrons which can be present in these subÂ¬shell is 2 + 14 + 6 + 10 = 32. Since the number of elements in a period corresponds to the number of electrons in the shells, therefore, sixth period should have a maximum of 32 elements.

Question-3: What does atomic radius and ionic radius really mean to you?

Solution: Atomic radius. The distance from the centre of nucleus to the outermost shell o electrons in the atom of any element is called its atomic radius. It refers to both covalen or metallic radius depending on whether the element is a non-metal or a metal.
Ionic radius. The Ionic radii can be estimated by measuring the distances between cations and anions in ionic crystals.