Electronic Configuration of Elements
The Electronic Configuration of Elements refers to the arrangement of electrons in different energy levels. The rule for the arrangement of electrons is governed by the following three laws:
- Aufbau Principle
- Hund’s Rule
- Pauli Exclusion Principle
Aufbau Principle
Aufbau is a German word that means ‘to build’. In Chemistry, Aufbau Principle states that the electronic arrangement of an element is done by filling electrons in ascending order of energy of subshell. It means electrons first enter subshells of lower energy and then of higher energy levels. The energy of a subshell is determined by adding Principal Quantum Number and Azimuthal Quantum Number i.e. (n+l). If two subshells have the same (n+l) value then the subshell having a lower value of n is of lower energy. Hence, electrons enter in the order of 1s, 2s, 2p, 3s, 3p, 4s, and 3d…..
Hund’s Rule
Hund’s Rule states that electrons in the subshell in the manner that in the first attempt of filling the subshell is half-filled i.e. each orbital has one electron and then the pairing of electrons is done. This is because half-filled and full-filled orbitals are more stable than incompletely-filled orbitals.
Pauli Exclusion Principle
Pauli Exclusion Principle states that an orbital can have a maximum of two electrons with opposite spin. This is because if two electrons of the same spin are in an orbital then all four quantum numbers will be the same which is not possible as per the Quantum Mechanical Model of the atom.
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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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