Welcome to Fundamental Chemistry, a book designed to guide undergraduate students through the essential concepts and principles that form the foundation of chemistry. Whether you are just beginning your journey into the world of molecules, atoms and reactions, or looking to deepen your understanding, this text aims to provide clarity, structure, and a strong conceptual framework to help you navigate the exciting and ever-evolving field of chemistry. Chemistry is often called the "central science" because it connects and integrates various disciplines such as physics, biology, and environmental science. Understanding its core principles not only lays the groundwork for advanced study but also equips you with the tools to approach real-world problems, from the development of new medicines to addressing environmental challenges. In this book, I have carefully structured the content to cater to a range of learning styles. The first chapters introduce fundamental concepts such as atomic structure, periodic trends, and chemical bonding, gradually building up like fundamentals of organic chemistry, stereochemistry. Throughout, emphasis is placed on understanding the "why" behind the principles, not just the "how," ensuring that you develop critical thinking skills and a deep, lasting understanding of the material. Illustrative examples, detailed diagrams, and practice problems accompany each topic, offering a hands-on approach to applying theoretical knowledge. Each chapter is designed to be self-contained, allowing you to progress through the material at your own pace, whether in a classroom setting or for independent study. Chemistry is a subject that often requires persistence and dedication and it is my hope that this book will help to make the journey easier, more engaging and most importantly, rewarding. Remember, every complex concept you master builds upon simpler ideas—so keep an open mind, stay curious, and embrace the challenge. This book has been framed as per NEP 2020 for IV years Choice Based Credit System (CBCS) degree program.