Tags
ATOMIC SPECTRUM OF HYDROGEN, BLACK BODY RADIATION, BOHR’S THEORY OF “H” ATOM, CLASSICAL THEORY, COMPTON EFFECT, Eigen equation, Eigen function. Eigen value., Eigen operator, Operators, PHOTOELECTRIC EFFECT, POSTULATES OF QUANTUM MECHANICS, Schrodinger Equation, Wave function
2.1. CLASSICAL CONCEPT
Treatment of the system based on classical Newton’s laws of motion.
(A) PHOTOELECTRIC EFFECT
- hν = wo + KE ; hν = hνo + ½ mv2 , wo = work function ; νo = Threshold frequency
Observations
The metal (an alkali metal like Cs) emits electrons only if a radiation of certain frequency is used.
- The KE of emitted electron is proportional frequency of light used.
- Energy of the radiation applied = energy used to remove electron + energy used by the electron to possess kinetic energy
- Number of electrons emitted is directly proportional to the intensity, I of the light.
(B) COMPTON EFFECT
Light falling on a beam of electron undergoes scattering. The scattered light has longer wavelength than the incident radiation.
(C) DIFFRACTION:
- Phenomenon characteristic of wave
- The experiment suggests the wave nature of electron
(D) BLACK BODY RADIATION
Black body = Perfect emitter and absorber of radiation-(Energy vs Wavelength).
Observations
- The wave length, λmax shifted to lesser value as temperature increases (visible to uv).
- λmax T = constant.
(E) ATOMIC SPECTRUM OF HYDROGEN
Emission spectrum-Line spectrum- Lymann (Transition from higher to 1st orbit). Balmer, Paschen, Brackett, Pfund Series of lines transition from higher to 2nd , 3rd 4th 5th orbit, respectively.
Observations
- Splitting of spectral lines when recorded using a high resolving spectrophotometer-presence of sub-energy levels called orbitals.
- Splitting of spectral lines in the presence of magnetic field-Directional properties of orbitals-Magnetic quantum number.
(F) BOHR’S THEORY OF “H” ATOM
- The electron revolves around the nucleus only in allowed (fixed) circular orbits.
- The angular momentum of the electron is an integral multiple of h/2л.
- These orbits are called stationary orbits and an electron revolving in these orbits does not radiate or absorb energy.
- An atom radiates energy when the electron in it jumps from higher energy to lower energy.
Clasical mechanics-Energy is continuous; Quantum Mechanics- Energy is discontinuous, quantized (fixed).
LINK-1: The file, in the following Link (LINK-1): QC–2.1: Classical Concept, gives an account of the concepts mentioned above.
⇒LINK-1:Please Click here ⇒ QC-2.1 Classical Concept
2.2: POSTULATES OF QUANTUM MECHANICS
- Postulate-1 (Wave functions)
Every system can be described by a well behaved wave function, Ψ
- Postulate-2 (Operators)
Each observable has a characteristic operator.
- Postulate-3 (Schrodinger Equation)
All systems satisfy an equation of the form HΨ=EΨ called Schrodinger Equation
- Postulate-4 (Eigen equation)
The observable of a system is given by the Eigen equation involving Eigen operator, Eigen function. and Eigen value.
- Postulate-5 (Average value or Expectation value )
The average or expectation value of an observable is given by the ratio of the corresponding integrals
LINK-2: The file, in the following Link (LINK-2): QC–2.2.Postulates of QM, gives an account of the QM postulates.
⇒LINK-2:Please Click here ⇒ QC–2.2-Postulates of QM
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Please go to CONTENTS for all the Articles in PoC: Click below
https://dradchem.wordpress.com/2015/06/22/properties-of-chemistry-poc-contents-2/