NCERT Solutions for Class 10 Science Chapter 5 Periodic Classification of Elements

The Science Chapter 5 Periodic Classification of Elements helps us to study various elements and their further classifications that different scientists tried out. The chapter begins with the classification of elements based on atomic masses or Dobereiner's Triads, which explains when the three elements in a triad are arranged to increase atomic masses, the atomic mass of the middle element was roughly the average atomic masses of the other two elements. The limitation to this classification was that Dobereiner could identify only three triads. He wasn't able to prepare triads of all the known elements.

Class 10 Science Chapter 5 Periodic Classification of Elements further discusses Newlands' Law of Octaves which states when elements are placed in order of increasing atomic masses, the properties of every eighth element are a repetition of the properties of the first element.

Mendeleev's Periodic Law states that "The physical and chemical properties of the elements are the periodic function of their atomic masses." Mendeleev's Periodic Table was based on the physical and chemical properties of elements along with their atomic masses. But this also had few limitations - No fixed position was assigned to hydrogen. Positions of isotopes of all elements were uncertain. The atomic masses do not increase in a regular manner in going from one element to the next.

Chapter 5 Periodic Classification of Elements explains well The Modern Periodic Table. It consists of 18 groups and 7 periods. Elements present in any one group contain the same number of valence electrons. The number of shells increases down the group. Elements present in any one period have the same number of shells. Each period marks a new electronic shell getting filled. Modern Period Law explains that 'Properties of elements are a periodic function of their atomic number. The Trends in the Modern Periodic Table are valency, atomic size, metallic and non-metallic characters, and electronegativity.