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Introduction to Radiochemistry
Forces in Matter and the Subatomic Particles
Nuclear science: study of structure, properties, and interactions of atomic nuclei at fundamental level.
nucleus – contains almost all mass of ordinary matter in a tiny volume
understanding behavior of nuclear matter under normal conditions
and conditions far from normal a major challenge
extreme conditions existed in the early universe, exist now in the core
of stars, and can be created in the laboratory during collisions
between nuclei (TRIUMF)
Nuclear scientists investigate by measuring the properties, shapes, and decays of nuclei at rest and in collisions.
This course covers low energy, or low temperature, nuclear science
=> properties of the nucleus
e- (lepton) bound in the atoms by the electromagnetic force
Neutrino observed in beta decay.
Quarks are bound in together by the strong force
in nucleons. Nuclear forces bind nucleons into
Gravitational interaction between the elementary particles
is in practice very small compared to the other three.
The forces of elementary particle physics are associated with the exchange of particles.
An interaction between particles is characterized by both its strength and its range.
1 fm = 10-15 m
Force between two objects can be described as exchange of a particle – particle transfers
momentum and energy between the two objects, and is said to mediate the interaction
graviton – not yet observed
pions or pi mesons – between nucleons
These are assumed to be elementary.
Hadrons: any strongly interacting subatomic particle; composed of quarks.
There are 2 categories:
Electron (e-) – Positron (e+)
Particles and antiparticles (such as the pair highlighted in pink) are created in pairs from the energy released by the collision of fast-moving particles with atoms in a bubble chamber. Since particles and antiparticles have opposite electrical charges, they curl in opposite directions in the magnetic field applied to the chamber.
e = 1.6022 x 10-19 C
1 Å = 10-10 m
1 fm = 10-15 m
mn = 1.6749 x 10-27 kg
= 939.55 MeV
= 1.008665 u
mp = 1.6726 x 10-27 kg
= 938.26 MeV
= 1.007276 u
The atomic nucleus consists of protons and neutrons
Protons and neutrons are generally called nucleons
Determines the Element
Determines the Isotope
Of course A=Z+N
Mass number A
Element symbol – defined by charge numberC is Carbon and Z = 6
So this nucleus is made of 6 protons and 6 neutrons
u: atomic mass unit
E = mc2
where energy usually expressed in MeV
Isotopes: same Z40Ca, 42Ca, 44Ca
often, ‘isotope’ used instead of ‘nuclide’
isotopes have same Z, so same number of electrons => same chemistry
use radioactive isotope in place of stable one – can monitor
decay for tracer studies
Isotones: same N40Ca, 42Ti, 44Cr
Isobars: same A42Ca, 42Ti, 42Cr
Isodiaphors: same neutron excess 42Ca, 46Ti, 50Cr
to how chemical properties are understood from the periodic chart
Natural Decay Chains
1.4 x 1010 y
(4n + 2)
4.5 x 109 y
7.04 x 108 y
End of Chapter 1