There are various postulates that we study in chemistry. A postulate is also called an axiom. These are those statements that are accepted by the world without any proof needed. These are the basic structures that are used to derive the theorems that are used now. When we develop any theory, any number of postulates can be used. The branch of chemistry was a set only. Even though when we move forward, we may find some flaws in these assumptions. 

Dalton’s Atomic Theory

The theory that was proposed by Dalton was related to the nature of matter that he came up with this scientific theory in 1808. This was a very important point in the history of science and basically, whole chemistry is based on this theory only. This theory stated that all matter is made up of very small particles that can not be further divided which means they are indivisible that are known as ‘atoms’. According to Dalton all the matter present on this planet is made up of these atoms.

Features of Dalton’s theory

• While we all knew that elements were identical, the atoms present inside them were actually of different sizes and masses. 
• This theory says that all the compounds that are made up of these atoms are only which are combined in different ratios. 
• He even said that when any chemical reaction took place the only change that used to happen was the rearrangement of the atoms present in the compounds. This was a drastic change in the history of modern science.

 Postulates

The postulates of Dalton’s Atomic Theory are as follows:

• All the matter is made up of small, indivisible particles that are known as atoms
• The atoms of a specific element are identical in mass, size, and even other properties. The atoms have different masses and sizes even though they are of the same element.
• Atoms of an element can neither be created nor be destroyed. They will remain the same, and even they cannot be divided further.
• Atoms combine in some whole number ratios that lead to the formation of compounds.
• Atoms present in a compound can be rearranged, combined, or separated in a chemical reaction.

 Limitations

• Dalton said that atoms are those particles that cannot be divided further which means they are indivisible but the theory of subatomic particles like protons, electrons, and neutrons proved this wrong. 
•  According to Dalton, all the atoms of an element have identical masses and sizes, but the discovery of isotopes proved this wrong; they stated that the same elements have different atomic masses.
• This theory stated that masses of the atoms should be different to have different mass numbers, but this was also proved wrong through the presence of isobars. They have the same mass number but are different elements.
• Dalton said that the atoms combine in whole-number ratios, but certain organic compounds are present that do not contain a whole-number ratio.
• This theory cannot tell about allotropes of an element like graphite and diamond both contain carbon.

Merits that we see in Dalton’s Atomic Theory

• Law of proportions, the law of conservation of mass, and the law of constant proportions is not violated by this theory
• This theory helps to distinguish between atoms, elements, and compounds.

Conclusion  

The conclusion that can be taken from the theory is that this was the first attempt to describe atoms with their properties. He was able to make a good conclusion. His theory was based on the theory of conservation of mass and the law of constant composition.

Atomic theory is always revised to keep in mind the existence of atomic isotopes and the conversions of mass and energy. Also, the discovery of subatomic particles shows that atoms can be divided into subatomic particles that are known as electrons, protons, and neutrons. He was so important to modern atomic theory that the atomic mass unit was given the name Dalton.

This is all about Dalton’s atomic theory; it contains these postulates and how these postulates are not up-to-date with modern science and what are the problems that are faced with this theory.