**Postulates of Dalton's Atomic Theory**

1) **All matter is made up of very small particles called atoms:** According to Dalton, matter is composed of indivisible and indestructible particles known as atoms. Atoms are the basic building blocks of matter and cannot be further divided into smaller particles. This postulate implies that all substances, whether they are solid, liquid, or gas, are ultimately made up of atoms.

2) **Atoms are not divisible, neither can they be created nor destroyed in a chemical reaction:** Dalton proposed that atoms are indivisible and cannot be broken down into simpler components. In a chemical reaction, atoms rearrange and combine with other atoms to form new substances, but the atoms themselves remain unchanged. This postulate is known as the law of conservation of mass, which states that the total mass of the reactants in a chemical reaction is equal to the total mass of the products.

3) **Atoms of the same element have the same mass and chemical properties:** Dalton suggested that all atoms of a particular element are identical in mass and chemical properties. This means that atoms of an element have the same number of protons, neutrons, and electrons, giving them the same atomic number and chemical behavior. For example, all hydrogen atoms have the same mass and exhibit similar chemical properties.

4) **Atoms of different elements have different sizes and chemical properties:** According to Dalton, atoms of different elements vary in size and chemical properties. Each element is composed of its own unique type of atom with distinct characteristics. For instance, the atoms of oxygen are different from the atoms of carbon in terms of size, mass, and chemical reactivity. This postulate explains the diversity of elements and their ability to form compounds with different properties.

Overall, Dalton's atomic theory laid the foundation of modern atomic theory and provided a framework for understanding the behavior and properties of matter. It emphasized the fundamental nature of atoms, their conservation in chemical reactions, and their role in determining the characteristics of different elements. Dalton's theory has been further refined and expanded upon over the years, but it remains a significant milestone in the field of chemistry.