Dalton’s Atomic Theory
John Dalton, a British Chemist proposed that every matter is made up of atoms. These atoms are indivisible and indestructible i.e. they can’t be broken down into smaller particles. He also suggested that all atoms of a particular matter are the same, but atoms of different elements differ in size and mass. This means atoms of each element are unique.
According to Dalton’s atomic theory, Chemical reactions occur at atomic level and involve the rearrangements of atoms in order to form the products. According to the postulates proposed in his theory, atomic structure is made up of atoms and they are the smallest particles responsible for chemical reactions to occur.
Postulates of Dalton’s Atomic Theory
- Every matter that exists is made of atoms.
- Atoms are indivisible.
- A particular element has only one type of atom in it.
- Atoms of different elements differ in size and mass.
- An atom has a constant mass that varies for every element.
- During a chemical reaction, atoms undergo rearrangement.
- Atoms can neither be created nor destroyed but can only be transformed from one form to another.
Dalton’s atomic theory was able to explain the Laws of chemical reactions successfully, named the Law of conservation of mass, Law of constant properties, Law of multiple proportions, and Law of reciprocal proportions.
Demerits of Dalton’s Atomic Theory
- This theory was not able to explain the existence of isotopes and isobars.
- No appropriate explanation was provided regarding the structure of atoms.
- Later the atoms were found to be divisible, and Dalton’s claim of atoms being indivisible was proved to be wrong.
The discovery of constituting particles of atoms led to a better understanding of chemicals, these constituting particles are called subatomic particles.
Atomic Structure
Atomic structure is the structure of an atom that consists of a nucleus at the center containing neutrons and protons, while electrons revolve around the nucleus. Atoms are made up of a very tiny, positively charged nucleus that is surrounded by a cloud of negatively charged electrons.
The earliest concept of atoms was given by Indian philosopher Maharshi Kanad who proposed that matter is made up of microscopic indestructible particles called ‘Parmanu’. A Greek philosopher named Democritus also initially claimed that matter is formed of atoms, and is credited with developing the concepts of atomic structure and quantum mechanics. Later in the 1800s, John Dalton a British Scientist put out the first atomic structure scientific theory.
This article explores the concept of atomic structure in detail, including the atomic models, and the concept of quantum theory.
Table of Content
- What is Atomic Structure?
- Atomic Models
- Dalton’s Atomic Theory
- Postulates of Dalton’s Atomic Theory
- Demerits of Dalton’s Atomic Theory
- Thomson’s Atomic Model
- Cathode Ray Experiment
- Observations of Cathode Ray Experiment
- Discovery of Electron
- Plum Pudding Model
- Drawbacks of Thomson’s Atomic Model
- Rutherford Atomic Model
- Alpha Ray Scattering Experiment
- Observation of Alpha Ray Scattering Experiment
- Conclusion of Rutherford’s model
- Discovery of Nucleus
- Limitations of Rutherford Atomic Model
- Bohr’s Atomic Model
- Postulates of Bohr’s Atomic Theory
- Limitations of Bohr’s Atomic Theory
- Quantum Mechanical Model of Atom
- Dual Behaviour of Matter
- Heisenberg Uncertainty Principle
- Schrodinger Wave Equation
- Postulates of Quantum Mechanical Model of Atom
- Quantum Number
- Principal Quantum Number(n)
- Azimuthal Quantum Number(l)
- Magnetic Quantum Number(ml)
- Spin Quantum Number(ms)
- Subatomic Particles
- Isotopes
- Atomic Structure of Isotopes
- Electronic Configuration of Elements
- Aufbau Principle
- Hund’s Rule
- Pauli Exclusion Principle
- Atomic Structure Class 11
Contact Us