Atomic and Nuclear Physics

Atomic Structure

ParticleLocationAbsolute Rest Mass(kg)Charge(C)
ProtonIniside the nucleus1.67*10-271.6*10-19
NeutronInside the nucleusapprox. equal to proton0
ElectronOrbiting atomic nuclei9.11*10-31-1.6*10-19


  • Isotopes have the same proton number but different mass number.

  • The Energy of a photon is:ΔE = E2-E1 = hc/λ = hf

    • Radioactivity

    RadiationPenetrationIonising abilityEffect of Mag. or Elec. Field
    Alpha αFew cm of air. Thin sheets of paperCauses intense ionisationDeflected slightly
    Beta βMany cm of air. Few mm of light metalsLees intense than alphaStrong Deflection
    Gamma γSeveral cm of dense metalsInteracts weakly with matterNo Defelction


  • The Radioactive decay law is: N = N0e-λt

  • The Half life is the time taken for half the number of radioactive nuclei present to decay

  • The Half life is found by:T1/2 = 0.693/λ

    The Nucleus

  • The Electronvolt can be defined as the quantity of energy gained by a particle carrying a charge equal to the charge on an electron when it is accelerated through a p.d of 1V.

  • The energy gained being accelerated through a p.d is: W = eV
  • The distance of closest approach in α scattering is: r = (1/4πε0)(QaQG/Ek)
  • The Wavelength of a high speed electron is: λ = h/p
  • If E>>Mec2 then: λ = hc/E
  • The relationship between Nuclear radius and Nucleon number A is: r = r0A1/3
  • Nuclei density is constant

    Nuclear Power

  • One atomic unit mass is: 1u = 1.661*10-27kg
  • Conversion to MeV:1u = 931.5MeV

  • The mass defect of a nucleus is the difference between the total mass of all its separate nucleons and the mass of the nucleus itself
  • The binding energy of a nucleus is the energy released when the nucleus is assembled from its constituent nculeons. It is equal to the energy needed to separate the nucleus into individual nucleons.
  • Einsteins mass and energy equation: E = mc2

    ParticleAtomic Mass (u)
    Proton(p)1.007276
    Neutron(n)1.008665
    Electron(e)0.000549
    Helium-3(3He)3.016030
    Helium-4(4He)4.002603
    Carbon-12(12C)12.000000
    Krypton-90(90Kr)89.9197
    Barium-143(143Ba)142.921
    Uranium-235(235U)235.04394


    Quantum Effects

  • Photoelectric emission is the emission of electrons from the surface of a metal when it is exposed to EM radiation of sufficiently high frequency.
  • The threshold frequency for a metal is the minimum frequency of EM radiation which can cause photoemission.
  • The Work function Φ of a material is defined as the work necessary to remove an electron from the surface of the material.

  • Einsteins photoelectric equation is: hf = Φ+Emax
  • The freshold frequency found by:f0 = Φ/h

  • The de-Broglie wavelength is:λ = h/p = h/mv = h/√(2eVm)