NucE 497A RAMP Class #2 1

NucE 497A RAMP Class #2 2 CHAPTER 2 – ATOMIC AND NUCLEAR PHYSICS 2.1 FUNDAMENTAL PARTICLES Physical world – combinations of subatomic (fundamental) particles

NucE 497A RAMP Class #2 3 Particles of interest to the NE: –Leptons – subject to weak nuclear forces (electron, positron, and neutrino) –Hadrons – subject to both weak and strong nuclear forces (proton and neutron – baryons)

NucE 497A RAMP Class #2 4 Hadrons – composed of quarks, which exchange gluons – strong nuclear forces For NE - we will consider a class of particles, without studying in detail their structure Appendix I – Units and conversion Factors Appendix II – Fundamental Constants and Data

NucE 497A RAMP Class #2 5 Electron: Rest mass m e = x kg Charge e= x coulombs Two types: negatrons (-e) and positrons (+e)

NucE 497A RAMP Class #2 6 Electron Annihilation

NucE 497A RAMP Class #2 7 Proton: Rest mass m p = x kg Positive charge equal to that of the electron

NucE 497A RAMP Class #2 8 Neutron: Rest mass m n = x kg Electrically neutral Not stable, except when is bounded into an atomic nucleus Free neutron decays (  -decay) to a proton with an emission of a negative electron and an antineutrino

NucE 497A RAMP Class #2 9 Photon: Zero rest mass Travels in vacuum with the speed of light (c=2.9975x10 8 m/sec) Particles associated with electromagnetic waves

NucE 497A RAMP Class #2 10 Neutrino: Zero rest mass No electrical charge Appears in the decay of certain nuclei Six types – electron neutrino and antineutrino

NucE 497A RAMP Class # ATOMIC AND NUCLEAR STRUCTURE Atoms – building blocks of the matter Atom – consist of nucleus, surrounded by cloud of moving electrons Nucleus – composed of protons and neutrons

NucE 497A RAMP Class #2 12 Atomic number – total number of protons in a nucleus – Z Total electrical charge - +Ze Neutron number – N Atomic mass number – nucleon number = total number of nucleons in a nucleus – Z+N=A

NucE 497A RAMP Class #2 13 Nuclides – Z A X (X – chemical symbol of the element) Isotopes – same Z and different A Isotopic abundance – in atom percent – a/o – percentages of the atoms of an element that are particular isotopes

NucE 497A RAMP Class # ATOMIC AND MOLECULAR WEIGHT Atomic weight – mass of neutral atom relative to the mass of a neutral 12 C The atomic weight of 12 C is taken to be = 12 M( Z A X) = 12x(m ( Z A X)/m( 12 C))

NucE 497A RAMP Class #2 15 Atomic weight of element: M =   I M i /100 Molecular weight – sum of the atomic weights of the constituent atoms Atomic and molecular weights – unit less numbers

NucE 497A RAMP Class #2 16 Gram atomic weight (gram molecular weight)-mole-amount of a substance having a mass in grams, equal to the atomic (or molecular) weight of substance Number of atoms (molecules) in a mole of any substance is a constant – Avogadro’s law

NucE 497A RAMP Class #2 17 Avogadro’s number – N A = x10 24 m( 12 C) = x g Atomic mass unit – amu – 1amu = (1/12) x m( 12 C) = x g

NucE 497A RAMP Class # ATOMIC AND NUCLEAR RADII Average atomic radii = 2x m Electron density increases with the increase of Z

NucE 497A RAMP Class #2 19 Nucleus radii: R=1.25 fm x A 1/3 Fm – fathometers (fm) = cm Uniform nuclear density (V of the nucleus is proportional to A)

NucE 497A RAMP Class # MASS AND ENERGY Einstein’s theory of relativity E rest = m o c 2 Mass and energy are equivalent and convertible

NucE 497A RAMP Class #2 21 Unit of energy – electron volt – eV Df. Kinetic energy of an electron, when it falls through an electrical potential of one volt 1eV= x joule MeV; KeV

NucE 497A RAMP Class #2 22 E total =mc 2 E kin = mc 2 -m o c 2 = m o c 2 [(1/  1-v 2 /c 2 )-1] For neutrons: E kin = (1/2) m o v 2 E kin  0.02 E rest

NucE 497A RAMP Class #2 23 For photons E=h H – Plank’s constant = 4.136x eV-sec - frequency of the electromagnetic wave, associated with photon

NucE 497A RAMP Class # PARTCLE WAVELENGTHS = h/p p – momentum of the particle p=mv p=  2moE kin = h/(  2moE kin )

NucE 497A RAMP Class #2 25 For neutrons: = (2.860x10 -9 )/  E For photons: = (1.240x10 -6 )/E