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Thomson’s model of atom- Every atom consists of charged sphere in which electrons are embedded like seeds in water melon | Its drawbacks:-couldn’t explain large angle scattering & the origin of spectral series. |
Rutherford’s model of atom-
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Limitations :-couldn’t explain the stability of the nucleus & the emission of line spectra of fixed frequencies.
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Distance of closest approach of the alpha particle in the α particle scattering experiment | |
Impact parameter of the alpha particle | |
Bohr’s model of atom | Limitations-applicable only for hydrogen like atoms & couldn’t explain the splitting of spectral lines. (not consider electro static force among the electrons) |
Orbit radius of the electron around the nucleus | |
Energy of the electron in the nth orbit of hydrogen atom | |
Angular momentum of electron in any orbit is integral multiple of h/2ð | L = mvr = nh/2π, n=1,2,3,… |
Wave number í | |
No of protons in a nucleus | |
Mass Number (A) Number of neutrons | No. of nucleons(protons + neutrons) in a nucleus A-Z |
Nuclear radius | R=R0 A1/3 |
Nuclear density | Ñ= 3m/4ðR03 |
Isotopes | Same Z & different A Ex, 1H2,1H3,1H1, & C12,C14,C16 |
Isobars | Same A & different Z [ 18Ar40,20Co40] & (1H3, 2H3) |
Isotones | Same no. of neutrons Mass of neutrons – 1H3, 2He4 |
Mas defect Δ m | Total Mass of nucleons – mass of nucleus |
Binding energy Eb | E= m c2 ( m= mass of reactants – mass of products) 1 a.m.u.= 931.5 Mev |
Radioactive decay law | dN/dt=-ëN -dW/dt= R= Activity, unit Bq. |
N =N0e-λt OR N=N0( ½)n , n = t/t1/2 |
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Half life | |
Mean life | τ= 1/λ |
3 types of radiations | Alpha,beta,gamma |
Nuclear fission | Splitting of a heavy nucleus into lighter elements.This process is made use of in Nuclear reactor & Atom bomb |
Nuclear fusion Fusing | Fusing of lighter nuclei to form a heavy nucleus.This process takes place in Stars & Hydrogen bomb. Controlled Thermonuclear Fusion In a fusion reactor-high particle density is requiredhigh plasma temperature of 109Ka long confinement time is required |
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