Question

Write Neils Bohr's postulates

Answer 1

Various postulates of Bohr’s atomic model are:

1. In an atom, the electrons revolve around the nucleus in certain definite circular paths called orbits, or shells.

2. Each shell or orbit corresponds to a definite energy. Therefore, these circular orbits are also known as energy levels or energy shells.

3. The orbits or energy levels are characterized by an integer not, where, n can have values 1, 2, 3, 4……. The integer not (= 1, 2, 3…) is called the quantum number of respective orbit. The orbits are numbered as 1, 2, 3, 4………… etc., starting from the nucleus side. Thus, the orbit for which n=1 is the lowest energy level.

The orbits corresponding to n = 1,2,3,4…..etc., are also designated as K,L,M,N……….etc., shells. When the electron is in the lowest energy level, it is said to be in the ground state.

Since, electronics can be present only in these orbits, hence, these electrons can only have energies corresponding to these energy levels, i.e., electrons in an atom can have only certain permissible energies .

4. The electrons present in an atom can move from a lower energy level (Elower) to a level of higher energy (Ehigher) by absorbing the appropriate energy. Similarly, an electron can jump from a higher energy level (Ehigher) to a lower energy level (Elower) by losing the appropriate energy.

The energy absorbed or lost is equal to the difference between the energies of the two energy levels, i.e.,

ΔE= Ehigher - Elower

Answer 2

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Neil's Bohr's Theory :

1) Centre of an atom is called Nucleus And Positive charge also present inside the Nucleus.

2) Electron Revolve around the Nucleus in fixed Radius and fixed Energy called Orbit or shell.

3) Each orbit is associated with Fixed Energy like K, L, M, N,O .....etc.

4) Electron Revolve only in Fixed orbit then there will be No loss or gain of energy Called Stationary Orbit.

5) Electron Revolve Only those orbit which have the Angular momentum (L) is inetragal multiple of h/2π

=> Angular momentum denote by " L " and Momentum by "P"

Hence, L = P x r

[mass x velocity = P ]

=> L = m x v x r

L = mvr

Then mvr = nh/2π

Here,

P = plank constant = 6.636 x 10^-34

n = number of shells

m = mass of object

v = velocity of electron

r = radius of object

6) Electron Have Quantisation Condition Means Available in fixed Amount and fixed path of angular momentum.

7) There will be No change in energy of shell.

8) If n of shell increase then there energy also increase and it's far from nucleus and Attraction of positive charge and negative charge also decrease.

9) When electron change his energy into higher to lower or lower to higher then energy will be absorbed or involved with present of electricity, heat etc. When energy Higher to lower then orbit also decrease the energy released and Lower to higher then absorbed energy.

10) Electron Always trie to remain In lowest energy level then electron Return back from higher into Lower so energy is emitted in form of radiation.Energy less then it's stability is high.