Bohr’s Atomic Model
Neils Bohr, a student of Rutherford proposed his model in 1915 to address the limitation of Rutherford’s Atomic Model. It is the most widely used atomic model and is based on Planck’s theory of quantization. It explains that electrons always move in fixed orbitals only, and they are not present everywhere in the atom. Bohr also explained that each orbit has a fixed energy level. An orbit is also called an Energy Shell. Rutherford only explained the nucleus of the atom while Bohr made changes to that model and added electrons and energy levels.
As per Bohr’s model, inside an atom, there is a small nucleus that is positively charged and is surrounded by negative electrons which move around in orbits which has specific energy level. To revolve in a particular orbit, electrons must possess energy equal to the energy level of the shell. Bohr found out that the larger the distance of an electron from the nucleus, the larger its energy which means the orbits near the nucleus has smaller energy and the shell farthest from the nucleus has larger energy.
Postulates of Bohr’s Atomic Theory
- Inside atoms, electrons are present in discrete orbits called “stationary orbits”.
- Quantum numbers are used to represent the energy levels of these shells.
- Electrons can go to higher levels by absorbing energy and move to lower energy levels by losing or emitting some energy.
- When an electron stays in its own orbit, no absorption or emission of energy takes place.
- Electrons revolve in these stationary orbits only.
- The energy of the stationary orbits is quantized.
Limitations of Bohr’s Atomic Theory
- It works only for single-electron species such as H, He+, Li2+, and Be3+
- When a more accurate spectrometer was used to observe the emission spectrum of hydrogen, each line spectrum was seen to be a combination of multiple smaller discrete lines.
- Bohr’s theory was unable to explain Stark and Zeeman’s effects.
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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
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