Atomic Theory is the scientific concept that all matter is made up of tiny particles called atoms. These atoms are the building blocks of everything around us, from the air we breathe to the food we eat. Each atom consists of a nucleus, containing protons and neutrons, surrounded by electrons that orbit the nucleus. This theory helps us understand the composition and behavior of different substances. Over time, many scientists, including John Dalton and Niels Bohr, have contributed to the development of Atomic Theory. Dalton proposed that atoms are indivisible and unique to each element, while Bohr introduced the idea of electron shells. Together, these ideas have shaped our understanding of chemistry and physics.