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Chapter 4 – Structure of the Atom

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:


The atomic composition leads to the atomic structure having a nucleus that is in the centre. In the nucleus, there are protons that are positively charged and neutrons that have no charge i.e they are neutral). In the heart of the nucleus, the negatively charged particles called electrons revolve. 

The story of the structure of the atom and quantum mechanics dates back to Democritus’ time, the man who initially proposed that atoms were formed of matter.

An element’s atomic structure consists of the nucleus and the configuration surrounding the e. Primarily, protons, neutrons and electrons form the atomic structure of matter. 

The atom’s nucleus, which is encircled by the electrons owned by the atom, is made up of protons and neutrons. An element’s atomic number represents the sum of protons in the nucleus. Neutral atoms consist of protons, electrons in equal quantities. However, to improve their steadiness, atoms may obtain or drop electrons and the charged entity is referred to as an ion. As they hold different numbers of electrons & protons, atoms of various elements have various atomic structures. This can be said as the explanation for the distinctive features of multiple parts.

With the assistance of atomic structures, many physicists sought to clarify the composition of the atom in the 18th and 19th centuries. Both of the models had eminence and demerits of their own and were central to the modern atomic model’s development. The scientists’ John Dalton, Sir Joseph John Thomson, Ernest Rutherford, and Niels Bohr’s atomic model made the most notable contributions to the field. 

Thomson’s Atom Structure 

In the early 1900s, Sir JJ Thomson presented his model that represented the structure of the atom. 

Bohr’s Atomic Model

The Bohr atom model was introduced by Neil Bohr in 1915. It came into being with the update of Rutherford’s atom model. Rutherford’s model introduced the nuclear model of an atom, stating that the nucleus (positively charged) is surrounded by negatively charged electrons.

Bohr changed this atomic structure model by demonstrating that electrons pass in fixed orbitals (shells) and not somewhere in between, and also demonstrated that each orbit (shell) has a fixed energy level. Rutherford ultimately clarified the nucleus of the atom, and Bohr changed the model into electrons and their energy ranges.


Valency is a measure of the potential of atoms or molecules to bind.

Atomic Number

The atomic number of the chemical element is the number of protons present in the nucleus of each atom of that element.

Mass Number

The mass number is the cumulative number of protons and neutrons (known collectively as nucleons) in the atomic nucleus.

Experiment on Cathode Ray 

The cathode ray experiment consists of a glass tube with two holes, one hole is for the vacuum pump and the other hole is for the inlet from which the pumping of the gas takes place. The vacuum pump is responsible for maintaining the “partial vacuum” inside the glass chamber. Using electrodes, i.e. cathode, a high voltage power supply is attached and the anode is fitted within the glass tube. 


  1. Thomson illustrated the structure of atoms as a positive circle in which negative electrons were confined, based on his cathode ray experiment’s results. 
  2. It is also pointed to as the “plum pudding model” since it can be related as a plum pudding where the pudding serves the atom with a positive charge and the electrons serve the plum bits. 
  3. Thomson’s atomic structure named atoms as electrically neutral, that is that the positive and negative charges were equal in magnitude.

Thomson’s atomic model fails to precisely explain the stability of an atom. It was therefore not necessary to put further observations of other particles (subatomic in nature) inside his atomic model. 

Rutherford’s Atomic Model 

  1. At the core of an atom, where the bulk of the charge and mass is concentrated, is the nucleus. 
  2. The atomic composition is spherical. 
  3. In a circular orbit, electrons revolve about the nucleus, close to the way planets revolve about the sun. 

Rutherford Atomic Model Drawbacks 

  • Suppose electrons revolve around the nucleus. They keep revolving in the nucleus until they lose some energy. Eventually, they lose all their energy and fall into the nucleus. 
  • If the ‘electrons’ are rotated continuously by the nucleus, a continuous spectrum is the sort of spectrum predicted. But in fact, what exists is a continuum of lines. 

Isotopes’ Atomic Structure 

The elements of an atom’s nucleus are nucleons. A nucleon is either a neutron or a proton. There is a distinctive number of protons in each element that is expressed by its distinctive atomic number. There may, however, be multiple atomic structures of an element, which vary in the total sum of nucleons. 

Such variation of elements with a particular number of nucleons (known as the number of masses) is referred to as element isotopes. Hence, the isotopes of an element have an equal number of protons but vary in the number of neutrons.

This chapter taught us about the structure of atoms. We learned about the different models, atomic number, and mass number of the atoms. We also learned about the valency of the atoms.

  • What are the 5 parts of an atom? 

Protons, electrons, and neutrons are components of an atom. A proton is charged positively and is found in the atom’s centre or nucleus.

  • Who gave the structure of an atom? 

Although the concept of the atom dates back to Democritus’ ideas, the first modern description of it as the fundamental building block of chemical structures was formulated by the English meteorologist and chemist John Dalton. 

  • What are the 4 types of atoms? 

In the solar system, the four most abundant atoms are hydrogen, oxygen, carbon, and nitrogen. 

  • Why is an atom neutral? 

On a single proton, the amount of charge is equal to the amount of charge that a single electron possesses. A proton and an electron have an equal quantity but an opposite charge type. The atom is thus defined as being electrically neutral if an atom comprises equal numbers of protons and electrons. 

  • What atom means?

Atoms, the smallest unit into which, without the release of electrically charged ions, the matter can be separated. It is also the smallest unit of matter with the distinctive characteristics of a chemical element.

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High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
  • Gravitation
  • Internal Energy
  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
  • Management Of Natural Resources
  • Mechanical properties of Fluids
  • Mechanical properties of Solids
  • Motion
  • Motion in a plane
  • Motion in a straight line
  • Moving Charges and Magnetism
  • Nuclear Energy
  • Nuclei
  • Oscillations
  • Our Environment
  • Paths of Heat
  • Physical world
  • Ray optics and optical instruments
  • Semiconductor Devices
  • Semiconductor Electronics: Materials, Devices and Simple Circuits
  • Simple Machines
  • Sound
  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
  • Static Electricity
  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
  • Chemistry of Transition and Inner Transition
  • Classification of Elements
  • Coordination Compounds
  • Cyanide, Isocyanide, Nitro compounds and Amines
  • Electrochemistry
  • Electrolysis
  • Elements, Compounds and Mixtures
  • Environmental Chemistry
  • Equilibrium
  • Ethers and Carbonyl compounds
  • Haloalkanes and Haloarenes
  • Hydrocarbons
  • Hydrogen
  • Ideal solutions
  • Introduction to Organic Chemistry
  • Ionic equilibria
  • Matter
  • Matter Around Us
  • Matter In Our Surroundings
  • Metallurgy
  • Metals And Non-Metals
  • Mole Concept and Stoichiometry
  • Natural Resources
  • Organic Chemistry – Basic Principles
  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
  • Biological Classification
  • Biomedical Engineering
  • Biomolecules
  • Biotechnology and its Applications
  • Biotic Community
  • Body Fluids and Circulation
  • Breathing and Exchange of Gases
  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
  • Cell Reproduction
  • Cellular Respiration
  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
  • Environmental Issues
  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
  • Heredity And Evolution
  • Heredity and Variation
  • How Do Organisms Reproduce?
  • Human Diseases
  • Human Eye And Colourful World
  • Human Health and Disease
  • Human Population
  • Human Reproduction
  • Hygiene
  • Improvement In Food Resources
  • Integumentary System- Skin
  • Kingdom Fungi
  • Kingdom Monera
  • Kingdom Protista
  • Life Processes
  • Locomotion and Movement
  • Microbes in Human Welfare
  • Mineral Nutrition
  • Molecular Basis of Inheritance
  • Morphology of Flowering Plants
  • Neural Control And Coordination
  • Nutrition in Human Beings
  • Organism and Population
  • Photosynthesis
  • Photosynthesis in Higher Plants
  • Plant Growth and Development
  • Plant Kingdom
  • Pollination and Fertilization
  • Pollution; Sources and its effects
  • Principles of Inheritance and Variation
  • Reproduction and Development in Angiosperms
  • Reproduction in Organisms
  • Reproductive Health
  • Respiration in Human Beings
  • Respiration in Plants
  • Respiratory System
  • Sexual Reproduction in Flowering Plants
  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
  • Structural Organisation of the Cell
  • The Endocrine System
  • The Fundamental Unit Of Life
  • The Living World
  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
  • Calculus – Differential Equations
  • Calculus – Integrals
  • Geometry – Area
  • Geometry – Circles
  • Geometry – Conic Sections
  • Geometry – Constructions
  • Geometry – Introduction to Euclid’s Geometry
  • Geometry – Three-dimensional Geometry
  • Geometry – Lines and Angles
  • Geometry – Quadrilaterals
  • Geometry – Straight Lines
  • Geometry – Triangles
  • Linear Programming
  • Matrices and Determinants
  • Mensuration – Areas
  • Mensuration – Surface Areas and Volumes
  • Number Systems
  • Number Systems – Real Numbers
  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
  • Pollution and conservation
  • Pollution Of Air And Water
  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
  • Patterns
  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
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