Dalton’s atomic theory postulates & limitations

CBSE 11th class chemistry, #Chapter-1, #Atomic structure, Learn all about Dalton's Atomic Postulates, the foundations of modern chemistry, in this informative video. Dive into the world of atoms and discover the principles that shaped the field of chemistry!
1.Elements and Atoms: Dalton theorized that all matter is composed of tiny, indivisible particles called atoms. These atoms are unique to each element and cannot be created, destroyed, or divided into smaller particles during chemical reactions.

2.Identical Atoms: Dalton proposed that atoms of the same element are identical in mass and properties, while atoms of different elements have different masses and properties.

3.Compounds and Chemical Reactions: According to Dalton, compounds are formed when atoms of different elements combine in simple, whole-number ratios. During chemical reactions, atoms are rearranged but never created or destroyed, which led to the law of conservation of mass.

4.Multiple Proportions: Dalton observed that when two elements form more than one compound, the masses of one element that combine with a fixed mass of the other element can be expressed as ratios of small whole numbers. This contributed to the law of multiple proportions.

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1. WHAT IS DALTON’S ATOMIC THEORY?

2. John Dalton was born in a poor weaver’s family in 1766 in England. He began his career as teacher at the age of twelve. Seven years later he became a school principal . Dalton left for Manchester to teach mathematics, physics and chemistry in a college. He spent most of his life there teaching and researching. In 1808, he presented his atomic theory which was a turning point in the study of matter He is known for his : Atomic theory , Dalton’s law , Law of multiple proportions , as well as research of color blindness . Who was John Dalton?

3. All matter is made of very tiny particles called atom . Which participate in chemical reactions. An atom of oxygen element An atom of hydrogen element Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms. Atoms are indivisible particles, which cannot be created or destroyed in a chemical reaction. Atoms can be rearranged, combined or separated in chemical reactions. All atoms of a given element are identical in mass and properties , but they differ from those of other elements. Identical Atoms in an Element : Atoms Cannot be Created or Destroyed : Postulates of Dalton's Atomic Theory Compounds Formed by Combining Atoms : Elements Consist of Atoms : 2 1 3 4

4. Limitations of Dalton’s atomic theory It does not account for subatomic particles:   Dalton’s atomic theory stated that atoms were indivisible . However, the discovery of  subatomic particles  (such as protons, electrons, and neutrons) disproved this postulate. It does not account for isotopes:  As per Dalton’s atomic theory, all atoms of an element have identical masses and densities. However, different isotopes of elements have different atomic masses (Example: hydrogen, deuterium, and tritium). It does not account for isobars:  This theory states that the masses of the atoms of two different elements must differ. However, it is possible for two different elements to share the same mass number. Such atoms are called isobars (Example:  40 Ar and  40 Ca). Elements need not combine in simple, whole-number ratios to form compounds:  Certain complex organic compounds do not feature simple ratios of constituent atoms. Example: sugar/sucrose (C 11 H 22 O 11 ). The theory does not account for allotropes:  The differences in the properties of diamond and graphite, both of which contain only carbon, cannot be explained by Dalton’s atomic theory. Carbon has 4 allotropes – graphite, diamond, fullerene and graphene