Bohrs Model Of Atom

Bohr’s Model of atom

Postulates of Bohr’s Model of atom:

1. An atom consists of positive charge (nucleus) and electrons are revolving around it in a circular orbit.

2. Electrons revolving in these orbits which have fixed value of energy hence these orbits are called as stationary states or energy levels.

3. Energy of different states can be calculated by :

En=21.8*10-19 Z2/n2 j/atom or 13.6 z2/n2 ev/atom or 1312 kJ/mole

4. Radii of stationary states can be calculated as r=ao n2/z where ao=52.1 pm.

5. Velocity of electron is given by the expression:

V= vo z/n where vo=2.18*108 cm/sec

6. As electrons can have discreet or fixed values of energy and not have their own values of energy they can be express by saying that energy of electron is quantised.

7. Like energy, angular momentum of electron is also have definite value and given as mvr= nh/2( pie) n lambda=(2pie) r

And lambda=h/p

From this we can get the value of mvr = nh/2 pie

8. When an electron in an atom are revolving in orbit without any loosing or gaining energy than atom is said to be in normal state or in ground state.

9. When an electron is emitting or absorbing energy than it means they are jumping from one level to another level which is subjected to high temperature and said to be in excited state.

Negative energy:

When an electron is at infinity there is no force of attraction and energy is taken as zero but when it comes closer to nucleus energy being released and hence it becomes negative.