Xam Idea Class 10 Science Chapter 5 Solutions: Periodic Classification Of Elements

Xam Idea Class 10 Science Solutions for Chapter 5 ‘Periodic Classification’ are based on the latest guidelines prescribed by CBSE. In Xam Idea Solutions all the necessary tips have been given wherever required with suitable examples. The solutions cover all the important concepts of the chapter from board exams point of view. All the solutions are made in simple and easy to understand language for your better understanding of the periodic table and its properties. All the solutions will help you revise the chapter in minutes during the board exams.

Xam Idea Class 10 Science Solutions Chapter 5 periodic classification id divide in 5 sections and includes a variety of questions such as short answer type questions, long answer type questions, HOTS and value-based questions also. There are a total of 98 questions included in this chapter. All the questions are included with the objective to enable you to think beyond the NCERT textbooks. You will be studying the different trends in the periodic table, the limitations or immolations of different scientists in their periodic laws and also the predictions of some scientists.

All the solutions for Xam Idea Class 10 Science Periodic Classification are strictly designed according to the latest CBSE syllabus. The exercises have been designed to generate the positivity while studying and help you in scoring well in the exams. Instasolv has made sincere efforts to make the solutions concise. All the solutions are carefully designed for your practice. The Instasolv provides with accurate content in order to avoid common errors made by Class 10 students during board exams. The main objective of our Xam Idea Solutions is to enhance your knowledge and help you in developing skills.

Important Topics of Xam Idea Class 10 Science Solutions Chapter 5 Periodic Classification

The chapter elaborates with the meaning of classification and the attempts made by different scientists in classifying elements, all the important laws to classify the elements, Dobereiner Triads, Newlands law of octaves, Meyer law, Mendeleev periodic law, the long form of the periodic table, periodicity, variation in periodic properties of the periodic table.


  • At first, in this chapter, you will study the periodic classification of elements. It is nothing but the division of elements into groups based on their properties. Elements with similar properties are placed in the same group.
  • Earlier, many attempts were made by different scientists in the classification of elements and some of them also succeeded in this theory.

Dobereiner’s Triads

  • Dobereiner was the first one to show the relationship between the properties of their elements and their atomic masses. These groups of three elements were called Dobereiner’s Triads.
  • According to the Dobereiner law of triads, “ when three elements of any particular triad were arranged in order of their increasing atomic masses, the atomic mass of the middle element was roughly the average of atomic masses of the other two elements.
  • When he made triads 35 elements were present. Lithium, sodium, potassium is one of the Triads of Dobereiner and the triad is also called alkali metals.
  • The limitation of his classification was that it failed to arrange all the known elements in the form of triads of elements having similar chemical properties.

Newlands Law Of Octaves

  • John Alexander Newlands arranged all the 56 elements known at that time in their increasing atomic mass.
  • According to Newlands Law of Octaves,” when elements are arranged in the order of increasing atomic masses, the properties of the 8th element (starting from a given element) are a repetition of the properties of the 1st element.
  • Newland law of octaves was applicable only up to the elements calcium i.e the lighter elements. After that, every 8th element did not possess similar properties as that of the first element.
  • Newland placed two elements in the same slot also placed unlike elements in the same column in order to fit all 56 elements into his table. Cobalt and nickel were placed in the same slot but have different properties.
  • Newland thought that only 56 elements will be existing in nature and that no other elements will likely to be discovered in future.
  • When Newland gave his law, noble gases were not discovered. However, when noble gases have not discovered the properties of the first and eight elements were not similar.

Mendeleev’s Periodic Table

  • There were 7 periods (horizontal rows) and 8 groups (vertical columns) in the original periodic table of Mendeleev.
  • In order to make sure that all the elements having similar properties fall in the same vertical column Mendeleev left some gaps in his periodic table and placed a few elements in the wrong order of their atomic masses.
  • He left some gaps because he knew that later on many new elements will be discovered and he also predicted the properties of several undiscovered elements on the basis of their positions in his table.
  • Noble gases could also accommodate Mendeleev’s periodic table without disturbing the other elements.
  • In his table, no fixed [position is given to hydrogen and the isotopes of the elements.
  • No regular trend in atomic masses. Position of some elements with lower atomic masses before the higher atomic masses is one of the features on Mendeleev’s periodic table.

Modern Periodic Table

  • In 1913, Henry Moseley showed that atomic number is a more fundamental property of classifying elements than atomic masses.
  • The physical and chemical properties of elements are periodic functions of their atomic number.
  • The modern periodic table contains 18 vertical columns called groups and 7 horizontal rows known as periods.

Trends In Modern Periodic Table

  • The number of valence electrons present in the outermost shell of an atom defines its Valency.
  • If you move from left to right in a period the valency first increases from 1 to 4 and then decreases to 0.
  • If you move from top to bottom in a group the valency remains the same because the number of valence electrons in each shell is the same.
  • The radius of an atom is known as its atomic size. The distance between the centre of the nucleus of the atom and its outermost shell is atomic size or radius.
  • On moving from left to right in a period the atomic size decreases because of the nuclear charge increases.
  • On moving from top to bottom in a group the atomic size increases as there is an increase in the nuclear charge.
  • The tendency of an atom to lose electrons defines its metallic characteristics.
  • In a period the metallic character decreases because the tendency to lose electrons is less.
  • In a group the metallic character increases as the tendency to lose electrons in a group is high.
  • Non-metallic character is referred to as the tendency of an atom to gain electrons.
  • Along the period from left to right the non-metallic character increases.
  • Along with the group from top to bottom the non-metallic character decreases.
  • The chemical reactivity of metals increases down the group because of the tendency to lose electrons increases.
  • The chemical reactivity of non-metals decreases down the group as the tendency to gain electrons decreases.

Exercise Discussion Of Xam Idea Class 10 Science Solutions Chapter 5 Periodic Classification

Very Short Answer Type Questions

This section includes 19 questions and each question carries 1 mark. In this section, you have to answer questions based on trends and periodic tables. The questions are based on Mendeleev’s law of periodic table, classification of the elements on the basis of atomic number and the Dobereiner’s basis of classifying elements. Definition of the groups or periods, a number of groups are there in the modern periodic table are some of the examples of questions that are discussed in this particular section.

Short Answer type Question

There are a total of 47 questions in this section and each question carries 3 marks. All the questions are extremely important for you from CBSE exams perspective. In this section, you will face questions based on the periodic table and their properties.

Long Answer Type Questions

This section contains 17 questions and each question carries 5 marks. In this section, the question id divide into 3 or 4 parts. How we calculate the valency of an element from the electronic configuration, how valency varies in a period, how valency changes down a group, give an account of the process adopted by Mendeleev etc are some of the examples of questions that are discussed in the section.


There are a total of 10 questions in this section which are a little bit tricky. Can any element have atomic number 2.5 or you might also have to identify the elements with the help of hints that are given in the question.

Value-Based Questions

There are a total of 5 questions in this section and each question is important. Some examples of questions are why there are groups or periods in the modern periodic table, why there is no position of hydrogen, why elements in the same period vary in their atomic size etc.

Why Use Xam Idea Class 10 Science Solutions Chapter 5 Periodic Classification by Instasolv?

  • Instasolv provides you with error-free Xam Idea Class 10 Science Solutions in simple and basic language.
  • All the Xam Idea solutions by Instasolv cover all the topics of the chapter are prepared by highly experienced subject experts.
  • These solutions include short tips and techniques so that you can solve each and every question in the exam.
  • These solutions also help you to develop your knowledge.