PROBLEMS IN GENERAL CHEMISTRY

APARUP ROY

Copyright © Aparup Roy All Rights Reserved. ISBN 978-1-63920-413-7 This book has been published with all efforts taken to make the material error-free after the consent of the author. However, the author and the publisher do not assume and hereby disclaim any liability to any party for any loss, damage, or disruption caused by errors or omissions, whether such errors or omissions result from negligence, accident, or any other cause. While every effort has been made to avoid any mistake or omission, this publication is being sold on the condition and understanding that neither the author nor the publishers or printers would be liable in any manner to any person by reason of any mistake or omission in this publication or for any action taken or omitted to be taken or advice rendered or accepted on the basis of this work. For any defect in printing or binding the publishers will be liable only to replace the defective copy by another copy of this work then available.

This book is dedicated to all the readers who has tremendous thirst to learn chemistry and it’s tough concepts clearly.

Contents Foreword

vii

Preface

ix

Acknowledgements

xi

1. Introduction

1

2. Big Bang Theory

3

3. Element & An Atom

6

4. Discovery Of Electrons

8

5. Discovery Of Protons & The Nucleus Of The

11

Atom 6. Bohr's Atomic Model & The Discovery Of

15

Neutrons 7. Structure Of An Atom, It's Atomic Number &

18

The Bohr-bury Scheme Of Electronic Configuration 8. Valence Electrons & The KÖssel-lewis Approach 21 To Chemical Bonding 9. Significance Of Lewis Symbols & Electron's In

24

An Atom 10. The Heisenberg Uncertainty Principle & The

27

Ionic Bonding 11. Ionic & Covalent Bonding

30

12. Numerical Problems

34

v

Foreword This book is an academic book entitled as "Problems in general chemistry" by the author name "Aparup Roy". This books gives a clear understanding of the chapter "Atomic structure and Chemical Bonding" with all the necessary details of the chapter being crept in. I also invite readers of this book to give their valuable suggestions to improve the book on my e-mail address that I have mentioned in my preface.

vii

Preface Preface: This book is the first edition of the book named “Problems in General Chemistry” by “Aparup Roy”. This book contains the chapter named “Atomic structure and Chemical bonding” with the full detailed description of the meaning of each of the term used in the book. Also it is being written with full detailed concept and understanding of the chapter. This book is intended as a textbook for students currently pursuing their studies in “High school or even higher grade”. This book contains some “numerical problems” connected with this chapter which will give a descent understanding of the chapter after solving them. Many numerical problems are also difficult to solveand may not be there in this chapter which would test outside knowledge of the students about this chapter. Any kind of errors or mistakes written in the book is being unintentionally crept in by the author. Suggestions for the further development and improvement of the book, as well as constructive criticism from learners and readers of this book, will be gratefully acknowledged. -APARUP ROY Email: [email protected]

ix

Acknowledgements I wanted to acknowledge my father "Arindam Roy" and my mother "Munmun Roy" who has continuously supported me to write this book and publish it. They also helped me by giving them their valuable suggestions to improve the book. So I am very much grateful to them.

xi

CHAPTER ONE

INTRODUCTION During the formation of our universe due to the “big-bang” theory lots of elements were created due to the immense energy and heat it generated. A lot of study in the field of chemistry in the topic of “Atomic structure” has been studied but still now no theory is being published which can give us the complete understanding of the atomic structure of an atom. Scientists from the very beginning in the course of history studied this topic and gave us various theories but no theory is there which can make us understand the structure of an atom completely. “Maharasi Kanada” in the 6th century B.C. in India says that matter consists of very tiny and indestructible particles which he called as “Paramanus”.Every element shows some of the different properties from that of the other element. But the first scientific theory about the structure of an atom was given by “John Dalton”. The main postulate’s of Dalton’s atomic theory are: Matter consists of very small and indivisible particles called atoms. Atoms can neither be created nor destroyed. The atoms of an element are alike in all respects but they differ from the atoms of other elements.

1

PROBLEMS IN GENERAL CHEMISTRY

Atoms of an element combine in small whole number ratio’s to form molecules. Atoms are the smallest units of matter that can take part in chemical reactions. Atoms of one element combine with atoms of another element in a simple ratio to form molecules of compounds. But according to the latest research done by the scientist most of the postulates given by John Dalton or Dalton’s atomic theory has been proved to be incorrect except that atoms take part in chemical reactions. Scientists in different parts of the world previously thought that atoms are indivisible particles and that it cannot be divisible by any means. But it was the study of static electricity which lead us to the understanding that atoms are made up of particles also known by the name of “Sub-atomic particles”. Sub-atomic particles in an atom are proton, neutron, electron. But still now there has been studies which shows that atoms are made up of nearly millions of particles namely mesons, quarks, etc. “Michael Faraday” showed that the flow of electricity is due to the flow of charged particles but it was first “G.J. Stoney” who first suggested the name of “electron” to this charged particle. (More of the discovery of the subatomic particles is being discussed in the book further). The electrons, protons and neutrons are called the “fundamental blocks of an atom”. These particles are the building blocks of all atoms of an element.

2

CHAPTER TWO

BIG BANG THEORY The Big Bang theory is the prevailing cosmological model explaining the existence of the observable universe from the earliest known periods through its subsequent largescale evolution. The model describes how the universe expanded from an initial state of high density and temperature, and offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure. Crucially, the theory is compatible with Hubble–Lemaître law—the observation that the farther away a galaxy is, the faster it is moving away from Earth. Extrapolating this cosmic expansion backwards in time using the known laws of physics, the theory describes an increasingly concentrated cosmos preceded by a singularity in which space and time lose meaning (typically named "the Big Bang singularity"). Detailed measurements of the expansion rate of the universe place the Big Bang singularity at around 13.8 billion years ago, which is thus considered the age of the universe. 3