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What are the postulates of Modern Atomic Theory?

Last updated date: 21st Jul 2024
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Hint: The Modern Atomic Theory, first stated by John Dalton, was built from Dalton’s atomic theory. It revolves around the fundamental role that atoms play in chemistry. There are five postulates of Modern Atomic Theory.

Complete answer:
The Modern Atomic Theory, built from Dalton’s Atomic Theory, was first stated by John Dalton in the year 1808.
It focuses on the concept of the fundamental role that atoms play in chemistry.
The five postulates of Dalton’s Atomic Theory are:
All matter is made up of tiny, indivisible particles called atoms.
All atoms of a specific element are identical in mass, size, and other properties. But, atoms of different elements have different properties and vary in mass and size.
Atoms can neither be created nor destroyed. Also, atoms cannot be divided into further small particles.
Atoms of different elements can combine with each other in fixed whole-number ratios and form compounds.
Atoms can be rearranged, combined, or separated during the process of chemical reactions.
The Modern Atomic Theory contradicts these postulates:
Atoms are divisible into small parts – protons, neutrons, and electrons
Atoms of the same element have different properties, which are called isotopes.
Atoms of different elements have the same properties, which are called isobars.
Atoms can combine in any ratio and not just fixed whole-numbers. For example, the reactions involving sugar molecules.
Finally, atoms can be destroyed and converted into energy.

Additional Information:
Dalton's Atomic theory was first stated and then Modern Atomic Theory was developed afterwards.
The Modern Atomic Theory helps calculate the number of protons and electrons in an atom, which in-turn help understand the properties of the atom.

Such questions can be tricky as it is easy to get confused between Dalton’s and Modern Atomic Theory. By remembering how the newer (i.e., Modern Atomic Theory) contradicted the old theory (Dalton’s), you will be able to remember the postulates as well.