Name: Law of Multiple Proportions
Uploaded: 2019-07-19
Duration: 6 min 43 s
Description: The Law of multiple proportions is applicable only when two elements combine to form two or more compounds. Watch this video to know how this law is applicable.

Question

What are the main postulates of Dalton’s Atomic Theory ? What were its limitations? How has the theory been modified ?

Accepted Answer

Postulates of Dalton’s Atomic Theory:

$(1)$ All matter is made of very tiny particles called atoms.

$(2)$ All atoms of a given element have identical properties, including identical mass. Atoms of different elements differ in mass.

$(3)$ A Compound is formed when atoms of different elements combine in a fixed ratio.

$(4)$ Chemical reactions involve the reorganization of atoms. These are neither created nor destroyed in a chemical reaction.

Limitations of Dalton theory:

$(1)$ Atoms are not individual particles. These are made of protons, neutrons and electrons which are subatomic particles.
(2) This theory does not hold for isotopes of an element as it proposed atoms of the same element possess the same mass but does not hold for it.
(3) This theory does not hold for isobars. Some elements whose masses are same but the atomic numbers are different are known as isobars.

On the basis of new experiments, Dalton's theory has been modified and the new postulates were given,

$(1)$ Atom is no longer considered to be indivisible.

$(2)$ Atoms of the same element may have different atomic masses, they known as isotopes.

$(3)$ Atoms of different elements may have the same atomic masses, known as isobars.

$(4)$ The ratio in which the different atoms combine with one another may be fixed and integral but may not always be simple.

$(5)$ Atom is the smallest particle that takes part in a chemical reaction.

$(6)$ Atom is no longer indestructible.

What are the main postulates of Dalton’s Atomic Theory ? What were its limitations? How has the theory been modified ?

Important Questions on Some Basic Concepts of Chemistry

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