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Structure of Atom

Subatomic Particles : Discovery and Characteristics

  • Macroscopic objects have particle character, so their motion can be described in terms of classical mechanics, based on Newton’s laws of motion.

  • Microscopic objects, such as electrons, have both wave-like and particle-like behaviour, so they cannot be described in terms of classical mechanics. To do so, a new branch of science called quantum mechanics was developed.

  • Quantum mechanics was developed independently by Werner Heisenberg and Erwin Schrodinger in 1926.

  • Quantum mechanics takes into account the dual nature (particle and wave) of matter.

  • On the basis of quantum mechanics, a new model known as quantum mechanical model was developed.

  • In the quantum mechanical model, the behaviour of microscopic particles (electrons) in a system (atom) is described by an equation known as Schrodinger equation, which is given below:


= Mathematical operator known as Hamiltonian operator

ψ = Wave function (amplitude of the electron wave)

E = Total energy of the system (includes all sub-atomic particles such as electrons, nuclei)

  • The solutions of Schrodinger equation are called wave functions.

Hydrogen atom and Schrodinger equation

  • After solving Schrodinger equation for hydrogen atom, certain solutions are obtained which are permissible.

  • Each permitted solution corresponds to a definite energy state, and each definite energy state is called an orbital. In the case of an atom, it is called atomic orbital, and in the case of a molecule, it is called a molecular orbital.

  • Each orbital is characterised by a set of the following three quantum numbers:

  • Principal quantum number (n)

  • Azimuthal quantum number (l)

  • Magnetic quantum number (ml)

  • For a multi-electron atom, Schrodinger equation cannot be solved exactly.

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