Write the postulates of Bohr’s atomic model.

Explanation

Postulates of Bohr.s atomic model
1. An atom has a small positively charged core where whole-of the mass of an atom is supposed to be concentrated. This core is called nucleus of the atom.
2. The electrons revolve round the nucleus in fixed orbits of definite radii. As long as the electron is in a certain orbit, it does not radiate any energy.
Therefore, the orbits in which electrons move are called stationary states. Each stationary state or the orbit has a definite amount of energy.
3. The electrons can revolve only in those orbits, in which its angular momentum is an integral multiple of `(h)/(2pi)`
`L=mvr=(nh)/(2pi)`
4. Electron can jump from higher energy level to lower energy level by radiating energy in the form of radiations Expression for the total energy in the nth orbit
The total energy of electron in the nth orbit is sum of its kinetic energy and P.E. in that orbit.
`K.E_(n)=1/2 mv^(2)`
But centripetal force required by an electron to revolve around the nucleus = Electrostatic force of attraction between an electron and nucleus.
But radius of nth orbit of hydrogen atom =`r_(n) epsilon_(0)(n^(2)h^(2))/(4pi^(2)e^(2)m)`
put value of `r_(n)` in eqn (v)
`E_("Total")=1/2 (e^(2))/(4pi epsilon_(0))=(4pi^(2)e^(2)m)/((4pi epsilon_(0)4 pi epsilon_(0)(n^(2)h^(2))`
`E_("total")= -2.17 xx10^(18)//n^(2)`
`E_(total )=(13.6)/(n^(2))eV`