# Aufbau principle

Aufbau principle: According to this principle, the electrons enter the various orbitals in the order of increasing energy. This means that electrons occupy the lowest orbital first and then the orbitals of next higher energy and so on. The different orbitals are filled up in the following order as given below.

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f,…

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# Pauli’s exclusion principle

Pauli’s exclusion principle: No two electrons in an atom can have the same value for the same set of four quantum numbers. Thus if two electrons have identical values of n ℓ and m it follows from this principle that they must differ in their spins i.e., +½ or -½. This means that two electrons can occupy the same sub-level and only if their spin are opposed. Natural…

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# Quantum numbers

Quantum numbers: These are numbers which are used to specify the location and energy of an electron and size, shape and orientation of the orbital to which a particular electron belongs.

Principal or total quantum number (n): This quantum number is identical with that used in Bohr Sommer field theory. It can have only non zero positive integral values.

i.e. n= 1, 2, 3, 4 ……….ꝏ

It quantizes…

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# De Broglie’s theory of wave nature of electrons

De Broglie’s theory of wave nature of electrons: Electron, like light has dual character (particle and wave like) de Broglie suggested the wave nature of electrons and derived the relation λ = h/p where λ is the wavelength and p the momentum of the electron and h is Plank’s constant. This relation is verified by interference and  diffraction experiments with electrons.

Heisenberg’s uncertainty principle: It is impossible to…

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# Nature of light and electromagnetic spectrum

Nature of light and electromagnetic spectrum:  According to Newton’s corpuscular theory, light is propagated as a stream of particles, called corpuscles. This could justify the phenomenon of reflection and refraction of light but failed to explain the phenomenon of diffraction, interference etc. Clerk Maxwell suggested that light waves are associated with both electric and magnetic fields, i.e. light may be described as  electromagnetic waves or radiations. there are…

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# Quantization

Quantization: means that a quantity does not vary continuously. The energy of an electron in an atom cannot have any arbitrary value but only certain characteristic values. ­A definite quantum of energy is accepted while moving from lower to higher energy level or lost while moving from higher to lower energy level, It does not accept any amount of energy nor does it lose energy continuously.

Quantum of…

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