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NCERT Solutions Class 9 Science - Chapter 4 Structure Of The Atom - PDF Download

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NCERT Solutions for class 9 science chapter 4 Structure of the atom by eSaral helps students to solve all the questions given in the NCERT class 9 textbook. You will find study material that has been prepared by eSaral experts with deep knowledge about the subject. Students who solve NCERT solutions for class 9 science will be able to get maximum marks in the class 9 science exam.

eSaral’s subject experts have prepared NCERT Solutions for science chapter 4 structure of the atom in simple and easy to understand language for the class 9 students, which will help them to understand the concept better. These NCERT solutions have been prepared on the basis of a concept-based approach and have been curated with the CBSE's answer method in mind. The panel has designed the NCERT textbook based on the latest developments in science and technology. Therefore, the allotted marks in the CBSE examinations are taken into account when preparing the answers so that students can get maximum marks.

NCERT Solutions for Class 9 Science Chapter 4 Topics:

Section Name

Topic Name


Structure of the atom


Charged Particles in Matter


The structure of an atom


How are electrons distributed in different orbits(shells)?




Atomic number and mass number



4.1 Charged Particles in Matter: The charged particles present in matter are responsible for a variety of physical and chemical processes. Electrons, protons and neutrons are the main types of charged particles present in the particle.

4.2 The structure of an atom: The atomic structure is the arrangement of the subatomic particles that make up an atom. In chemistry and physics, the atomic structure is one of the fundamental concepts. The Bohr model is a model used to visualize the structure of the Bohr atom. The Bohr model describes the structure of electrons, protons, and electrons in an atom.

Subtopics covered in the section 4.2 The structure of an atom:

      4.2.1 Thomson’s model of an atom

      4.2.2 Rutherford’s model of an atom

      4.2.3 Bohr’s model of atom

      4.2.4 Neutrons

4.3 How are electrons distributed in different orbits(shells)?: The electron configuration is the arrangement of electrons in various orbits or shell configurations around an atom's nucleus. The electron configuration is governed by the principles of quantum mechanics. The principles of quantum mechanics help explain how electrons occupy various energy levels and subshells within those levels.

4.4 Valency: Valency, or combining capacity, is the number of atoms that an element’s atom can form with another atom. It describes how an element interacts with other atoms to form molecules and compounds. Valency is a fundamental concept in the study of chemical bonding and molecular and compound structure.

4.5 Atomic number and mass number: Atomic number and mass number are fundamental numbers in atomic and nuclear physics, and are used to identify and describe various isotopes and elements.

Subtopics covered in the section 4.5 Atomic number and mass number:

      4.5.1 Atomic number

      4.5.2 mass number

4.6 Isotopes: Isotopes are atoms of an element that share the same number (and therefore atomic number) of protons in their nucleus, but a different number of neutrons. Because of the difference in number, isotopes have different mass numbers. Isotopes of a certain element have similar chemical properties because they share the number of electrons in their nucleus and the same electronic configurations.

Subtopics covered in the section 4.6 Isotopes:

      4.6.1 Isobars

Key Features of Class 9 Science Chapter 4 

  • The nucleus is the core of an atom. It contains the protons and the neutrons. The nucleus accounts for almost all the mass of an atom, but it occupies a tiny volume compared to the whole atom.

  • The protons in the nucleus are positively charged. The number of protons determines the atom's identity.

  • The neutrons in the nucleus are neutral. They have the same relative mass as the protons, but they do not carry an electric charge.

  • The electrons in the nucleus are negatively charged. The electrons in the electron shells have a specific amount of energy, with the innermost shell having the lowest amount of energy. Higher-energy shells have more energy than lower-energy shells.

  • Each energy level is separated into different subshells and each subshell contains one or several orbitals. The orbitals are regions where electrons are most abundant. For example, the "s" subshell contains one spherical orbital, and the "p" subshell contains three dumbbell-sized orbitals.

  • The electron configuration of the electrons in the energy levels and subshells is called the electron configuration. The electron configuration follows the principles of Aufbau, Pauli exclusion, Hund's rule, and others.

  • The atomic number (Z) of an element is its number of protons. This number uniquely identifies the element on the periodic table and determines its position.

  • The mass number (A) of an atom is the sum of protons and electrons in the nucleus. The mass number of the same element has isotopes.

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Frequently Asked Questions

Question 1: What is the structure of an atom?

Answer 1: An atom has a nucleus in the middle that's made up of protons and electrons. The electrons go around the nucleus in different energy levels or shells.

Question 2: What are valence electrons?

Answer 2: Valence electrons are the electrons in the lowest energy state of an atom. Valence electrons are essential for chemical bonding and reactions.



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