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Atomic Physics

Atomic physics (or atom physics) is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and the processes by which these arrangements change.

Atom as a whole is neutral, that is positive charges and negative charges are equal.

The positive charge and the whole mass is uniformly distributed like a cake and electrons embedded appear as cheeriest in the cake. Therefore, it is also called plum pudding model.

It cannot explain a – particle scattering and spectrum of an atom. Leonard in 1903 suggested that atom is made up of tiny particles called electrons and similar tiny particles carrying positive charge. He could not explain why the heating of metals does not eject positively charged particles.

The whole positive charge is concentrated in a small region called nucleus. The size of the nucleus is of the order of 10-15m or I fm.

The electrons revile around the nucleus in circular orbits. The size of an atom is 10-10m. There exists a large empty space around the nucleus.

Atoms are electrically neutral.

Distance of closest approach

Impact parameter

It could not explain why the electrons revolving around the nucleus do not fall into the nucleus following a spiral path, that is, it could not explain stability of the atom.

The number of particles scattered through an angle θ is given by

The electrons move around the nucleus in circular orbits.

The orbits are stable called stationary orbits. They have special values of radii such that the angular momentum is quantized that is,

The energy is emitted when electrons make a transition from higher to lower orbit and energy is absorbed when electrons jump from lower to higher orbit.

The centripetal force is equal to the electrostatic force.

Radius of nth orbit

Binding energy of nth orbit

Sommer feld’s model the electrons revolve around the nucleus in elliptical orbit. The mass of the electron changes with the velocity relectvistically

The total angular momentum of an electron is the resultant of orbital angular momentum and radial angular momentum. These two angular momentums are separately quantized.

De – Broglie theory the electrons revolve around the nucleus in stable circular orbits in the form of stationary waves.

Only those circular orbits are possible whose circum ferrous is integral multiple of de- Broglie wavelength associated with the electron, that is,

Velocity of electron in the nth orbit

Angular frequency of electron

Electric current due to electron motion in nth orbit

Magnetic induction produced in the nth orbit

Magnetic moment produced in the nth orbit

Rydberg constant

In balmer series

The number of waves N in distance d is

**Thomson’s model (1898)**Atom as a whole is neutral, that is positive charges and negative charges are equal.

The positive charge and the whole mass is uniformly distributed like a cake and electrons embedded appear as cheeriest in the cake. Therefore, it is also called plum pudding model.

It cannot explain a – particle scattering and spectrum of an atom. Leonard in 1903 suggested that atom is made up of tiny particles called electrons and similar tiny particles carrying positive charge. He could not explain why the heating of metals does not eject positively charged particles.

Rutherford’s modelRutherford’s model

The whole positive charge is concentrated in a small region called nucleus. The size of the nucleus is of the order of 10-15m or I fm.

The electrons revile around the nucleus in circular orbits. The size of an atom is 10-10m. There exists a large empty space around the nucleus.

Atoms are electrically neutral.

Distance of closest approach

**r – 2Ze**^{2}/ 4πε_{0}(KE)Impact parameter

**b = Ze**^{2}cot ∅^{2}/ 4πε_{0}(KE)It could not explain why the electrons revolving around the nucleus do not fall into the nucleus following a spiral path, that is, it could not explain stability of the atom.

The number of particles scattered through an angle θ is given by

**N (θ) a Z**^{2}/ sin^{4}(θ^{2}) (KE)^{2}**Bohr’s model**The electrons move around the nucleus in circular orbits.

The orbits are stable called stationary orbits. They have special values of radii such that the angular momentum is quantized that is,

**mvr = nh where h = h/2π.**The energy is emitted when electrons make a transition from higher to lower orbit and energy is absorbed when electrons jump from lower to higher orbit.

The centripetal force is equal to the electrostatic force.

Radius of nth orbit

**rn = n**^{2}ε_{0}h^{2}/ πmze^{2}Binding energy of nth orbit

**E**_{n}= mZ^{2}e^{4}/ 8ε^{2}_{0}h^{2}n^{2}Sommer feld’s model the electrons revolve around the nucleus in elliptical orbit. The mass of the electron changes with the velocity relectvistically

**M = m**_{0}/ 1 – v^{2}/ c^{2}The total angular momentum of an electron is the resultant of orbital angular momentum and radial angular momentum. These two angular momentums are separately quantized.

De – Broglie theory the electrons revolve around the nucleus in stable circular orbits in the form of stationary waves.

Only those circular orbits are possible whose circum ferrous is integral multiple of de- Broglie wavelength associated with the electron, that is,

**2πr – nλ**Velocity of electron in the nth orbit

**Vn = 2πZe**^{2}/ 4πε_{0}nh = c / 137 z /n = 2.2 x 10^{6}z n**α = 2πe**ch is called fine structure constant =^{2}/ 4πε_{0}**1/137.**Angular frequency of electron

**= 8π**^{2}Z^{2}e^{4}m / (4 πε_{0})2 n^{3}h^{3}= 4.159 x 10^{6}Z^{2}/ n^{3 }rads^{-1}Electric current due to electron motion in nth orbit

**In = 4πZ**^{2}e^{5}m^{2}/n^{3}h^{3}(4πε_{0})^{2}= 1.06 Z^{2}/ n^{3}mA.Magnetic induction produced in the nth orbit

Bn = μBn = μ

_{0}In / 2rn = 8π^{4}Z^{3 }e^{7}m^{2}/ n^{5}h^{5}(4πε_{0})^{3}= 12.58 Z^{3}/ n^{5 }Tesla.Magnetic moment produced in the nth orbit

**Mn = ehn / 2 m = ehn / 4πm = 9.26 x 10**Bohr magneton.^{-24}n Am^{2}= n**KE of electron = e**

PE of electron = - 2KE = e

Binding energy of electron = KE + PE = En = - e^{2}Z^{2}/ 8πε_{0}rn = 13.6Z2 / n^{2}eV.PE of electron = - 2KE = e

^{2}Z^{2}/ 4πε_{0}rn = - 27.2Z2 / n^{2}eVBinding energy of electron = KE + PE = En = - e

^{2}Z^{2}/ 8πε_{0}rn = 13.6Z2 / n^{2}eV.**Lonisation potential = En / e = 13.6Z2 / n**^{2}VRydberg constant

**R = me**_{4}/ 8ε^{2}_{0}ch_{3}= 1.09737 x 10^{7 }m^{-1}In balmer series

**λ(nm) = 364.56n2/n**representation of waves associated with orbital electrons in an atom^{2}– 4 where n = 3, 4, 5, ……The number of waves N in distance d is

**N = d/λ.****Services:-**Atomic Physics Homework | Atomic Physics Homework Help | Atomic Physics Homework Help Services | Live Atomic Physics Homework Help | Atomic Physics Homework Tutors | Online Atomic Physics Homework Help | Atomic Physics Tutors | Online Atomic Physics Tutors | Atomic Physics Homework Services | Atomic PhysicsTo book a free session write to:- tutoring@thehomeworkhelp.co.uk or call 8185279935