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NCERT Solutions Class 11 Chemistry - Chapter 2

JEE Mains & Advanced

NCERT Solutions Class 11 Chemistry - Chapter 2 deals with structure of atom. Class 11 Chemistry - Chapter 2 contains a number of questions in the exercise of the chapter. NCERT Solutions are created to answer all the questions asked in chapter 2 of the class 11 chemistry textbook. In chapter 2, the structure of atom will be fully explained. The main purpose of creating the NCERT solution is to help the students to concentrate on the important concepts and to learn them well.

After studying this chapter you will able to 

  • Learn about the discoveries of electrons, protons and neutrons and their properties

  • Describe the atomic models of Thomson, Rutherford and Bohr

  • Understand the essential properties of the quantum mechanical model of atoms

  • Understand the electromagnetic radiation and Planck's quantum theory

  • Describe the photoelectric effect and the properties of atomic spectra

  • State de Broglie's relation and Heisenberg's uncertainty principle

  • Define an atomic orbital using quantum numbers

  • State Aufbau's principle, Pauli's exclusion principle and Hund's maximum multiplicity rule

  • Write the electronic configurations of atoms.

NCERT Solutions for Class 11 Chemistry Chapter 2 Sections

Section Name

Topic Name


Structure of atom


Discovery of subatomic particles


Atomic Models


Developments leading to the bohr’s model of atom


Bohr’s model for hydrogen atom


Towards quantum mechanical model of the atom


Quantum mechanical model of atom

2.1 Discovery of sub-atomic particles: Subatomic particles have been around for centuries and there have been lots of different scientists and experiments that have led to their discovery.

In this section, following subtopics will be discussed

  • Discovery of electrons

  • Charge to mass ratio of electron

  • Charge on the electron

  • Discovery of protons and neutrons

2.2 Atomic models: As we've gotten more and more familiar with the atom, our understanding of how it works has grown. Some of the most important atomic models have been around for a while and have had a big impact on the state of atomic theory.

In this section, following subtopics will be discussed

  • Thomson model of atom

  • Rutherford’s nuclear model of atom

  • Atomic number and mass number

  • Isobars and isotopes

  • Drawbacks of rutherford model

2.3 Developments leading to the Bohr’s model of atom: Bohr's model for the atom revolutionized the way we understand the structure of atoms. It was based on a bunch of different discoveries and theories, and here are some of the key steps that led to it.

In this section, following subtopics will be discussed

  • Wave nature of electromagnetic radiation

  • Particle nature of electromagnetic radiation: Planck’s quantum theory

  • Evidence for the quantized* Electronic energy level: atomic spectra

2.4 Bohr’s model for hydrogen atom: The hydrogen atom model, developed by Niels Bohr, revolutionized the field of atomic physics by providing a logical explanation for the spectrum of the hydrogen atom.

In this section, following subtopics will be discussed

  • Explanation of line spectrum of hydrogen

  • Limitation of bohr’s model

2.5 Towards quantum mechanical model of the atom: The quantum mechanical model (or wave mechanical model or quantum model) of the atom was the first step beyond Bohr’s model and classical physics, introducing the wave functions of electrons and providing a new understanding of atomic behavior.

In this section, following subtopics will be discussed

  • Dual behaviour of matter

  • Heisenberg’s uncertainty principle

2.6 Quantum mechanical model of atom: The quantum mechanical model (or wave mechanical model) of the atom describes the behavior of electrons in atoms. It is based on the fundamental principles of quantum mechanics, and describes the atomic structure, the behavior of electrons, and elements' properties.

In this section, following subtopics will be discussed

  • Orbitals and quantum numbers

  • Shapes of atomic orbitals

  • Energies of orbitals

  • Filling of orbitals in atom

  • Electronic configuration of atoms

  • Stability of completely filled and half filled subshell

Key Points of Class 11 Chemistry NCERT Solutions Chapter 2

  • Atoms are the fundamental elements. They’re the smallest part of an element that undergoes chemical reactions. John Dalton proposed the first atomic theory in 1808, which held atoms to be indivisible particles of matter. At the end of the 19th century, experimentally demonstrated that atoms are indivisible and made up of three elementary particles: electrons, protons, and neutrons. Sub-atomic particles were discovered and led to the development of various atomic models to describe the structure of atoms.

  • In 1898, physicist Thomas proposed that the atom is made up of a single ball of positive electricity, with electrons built into it. However, this model of the atom, where the mass is thought to be spread out evenly across the atom, was challenged by physicist Albert Einstein in 1909 with his famous alpha particle scattering experiment. Einstein's results showed that the atom is actually made up of a tiny, positively charged nucleus at its center, with electrons moving around it in circles.

  • An orbit is a well-defined path, and it can only be completely defined if we know the exact position of the electron and its velocity at the same time. This is impossible according to Heisenberg's uncertainty principle. Bohr's hydrogen atom model therefore not only disregards the dual behaviour of the electron, but it also violates Heisenberg's Uncertainty Principle.

  • Schrödinger's equation, first proposed in 1926, describes the distribution of electrons in the universe and the energy levels that can exist in atoms. It is based on the idea of wave and particle duality, which is also supported by Heisenberg's uncertainty principle.

  • According to the atom’s quantum mechanical model, the distribution of electrons in an atom that contains many electrons is called the shell distribution. Shells are thought to consist of one shell or more subshells, and subshells are thought to be one or more orbitals that the electrons occupy.

Benefits of Downloading the PDF of NCERT Solutions Class 11 Chemistry Chapter 2 Structure of Atom

There are several Benefits of Downloading the PDF of NCERT Solutions Class 11 Chemistry Chapter 2 Structure of Atom

  • Comprehensive explanation: NCERT Solutions provide comprehensive and step by step explanations for every question and concept of the chapter, which helps students to understand the subject better and clear any doubts they might have.

  • Accurate and reliable solutions: The NCERT Solutions have been prepared by experts in the subject matter and experienced teachers to provide accurate and reliable answers.

  • Exam preparation: Class 11 is a very important year for students, as it prepares them for higher studies. Referring to NCERT Solutions will help students to prepare for exams well and do well in their assessment.

  • Time saving: The solutions can save time as students don’t have to search for answers from several sources. They can easily access the solutions in one place and complete the assignments efficiently.

  • Revision and Reinforcement: Students can use the these solutions for revision purposes to reinforce what they learned in a particular chapter.

  • Improving Problem-Solving Skills: Students can work through the solutions to enhance problem-solving abilities and learn how to effectively approach various types of questions.

  • Encouraging Self-Learning: PDF format allows students to learn at their own speed and convenience, promoting self-education and independent thinking.

To sum up, downloading the free pdf of NCERT solutions for class 11 chemistry chapter 2 can be very useful for students as it gives complete and accurate answers, helps in preparing for the exam, and improves their knowledge of atomic structure and related ideas.

Frequently Asked Questions

Question 1: Explain the Bohe’s model of the atom?

Answer 1:  According to Bohr's model, electrons move around the nucleus in particular energy levels or shell configurations. Electrons can move between these configurations by taking in or releasing energy in separate packets (quanta). Bohr's model explains the line spectrum of various elements.

Question 2: What is the Heisenberg Uncertainty Principle?

Answer 2: German physicist Werner Heisenberg stated uncertainty principle in 1927 as the result of the dual behaviour of matter and radiation. Heisenberg's uncertainty principle states that it is not possible to know the exact position and exact velocity of an electron at the same time.