NCERT Solutions for Class 11 Chemistry Chapter 3

Even though atomic mass is related to the nucleus that is situated in the center of the atom, it is not ideal to classify elements based on that. This is because the properties of the elements are dependent upon the electronic configuration related to the atomic number. Change in the electronic configuration of all elements leads to changes in their properties. It is a more easy and efficient way to classify elements based on their chemical and physical properties. Atomic number is a better option for classifying elements than atomic mass.

The Mendeleev’s Periodic Table was framed by Dimitri Ivanovich Mendeleev. The table has elements arranged in vertical columns called groups and horizontal rows called periods. 

• The table has a total of nine rows which are named in Roman numerals (I, II, III, IV, V, VI, VII, VIII, zero). The eighth group has nine elements in it. These elements are arranged in three triads. The group name zero consists of gases and elements that have zero valency.
• There are a total of 7 periods in Mendeleev’s Periodic Table.

Basis of periodicity is the major difference between Mendeleev’s Periodic Law and the Modern Periodic Law. Mendeleev’s Periodic Law says that the basis of periodicity is the atomic mass of the elements. Mendeleev had put elements having the same properties into a group. According to the Modern Periodic Law, the basis of periodicity is the atomic number of elements. Arranging elements based on atomic numbers in the periodic table was the right thing to do as per Henry Moseley. The properties of elements were considered a periodic function of their atomic masses by Mendeleev while as per Modern Periodic Law properties of elements were considered a periodic function of their atomic numbers. 

Class 11 Chemistry Chapter 3 NCERT Solutions are one of the best guides out there. Incorporated with all types of exercises, the Class 11 Chemistry Chapter 3 Solutions help students learn all the important concepts. Solving questions will assure that students have thoroughly studied everything in this chapter. This will assure that they score well in the exam. 

British Chemist John Newlands arranged elements in ascending order based on atomic masses in the year 1864 in such a way that every eighth element had similar properties. This observation led to the formulation of Newlands’ Law of Octaves. 

This law said that when elements are arranged in the increasing order of their atomic masses, every eighth element has similar properties. Newlands compared this similarity of every eighth element to octaves of music where every eighth note is comparable to the first. However, Newlands’ Law of Octaves had the following limitations as well;

• Elements that had dissimilar properties were grouped together.
• Classification under the Newlands’ Law of Octaves was successful only until the calcium element. After calcium, every eighth element lacked the same properties that the element placed above it in the same group possessed. 
• The discovery of noble gases disrupted the entire table as including the noble gases elements disturbed the entire arrangement. 
• Multiple elements were fit into the same slot. Eg: cobalt and nickel were placed together. 
• This method of classification was not ideal since it did not leave room for new elements as other elements that were later discovered could not fit into the octave pattern. At the time of Newlands’ discovery, only 56 elements were known. However, 118 elements are known to us today.

The ability of an atom that is a part of a given chemical compound to attract shared electrons is called electronegativity. Measuring electronegativity is not possible quantitatively like ionization enthalpy and electron gain enthalpy, hence it is a qualitative measure. No given element’s electronegativity is constant. It varies depending on the element it is bound to. To get more in-depth knowledge students can refer to the NCERT Solutions for Chapter 3 by downloading the solutions for free from Extramarks. 

The current form of the Periodic Table is based on the Modern Periodic Law. Elements are arranged in the increasing order of their atomic numbers in the present form of the periodic table. Therefore, the modern periodic table with 18 vertical columns (called groups) and 7 horizontal rows (called periods) is the present form of the periodic table. 

Students need to have a thorough understanding of the periodic tables that have evolved throughout the ages. Hence, students should be able to differentiate the multiple periodic tables that are a part of this chapter. They need to be prepared well enough to list down all the properties of the elements that each periodic table includes. They need to practise well for this. NCERT Solutions for Class 11 Chemistry Chapter 3 will cover exercises that will help students score high marks in their exams.