Nuclear Chemistry

Nuclear Chemistry
Diane Won
Christa Pamperien
Sarah Logsdon
Section 1: Radioactivity
 Nucleons: a particle found in the nucleus of
the atom
 Radioactive: nuclei that spontaneously emit
 Radionuclides: nuclei that are radioactive
Unstable, spontaneously emit particles and
electromagnetic radiation
 Radioisotopes: atoms containing
Nuclear Equations
 Alpha particles: helium-4 particles
Stream of these is called alpha radiation
 Reactant and product nuclei are represented by
giving their mass numbers and chemical symbol
 The totals of the mass numbers on both sides of
the equation are equal
 The totals of the atomic numbers on both sides
are also equal
238 U  234 Th + 4 He
Nuclear Equations Con’t
 What product is formed when radium-226
undergoes alpha decay
 22688Ra  AZX + 42He
 226 = A + 4
 88 = Z + 2
 A = 222 and Z = 86
 22688Ra  22286Rn + 42He
Types of Radioactive Decay
 Alpha particles:
 Beta particles:
 Gamma particles:
Types of Radioactive Decay Con’t
 Positron emission: has the same mass as an
electron but on opposite charge 01e
11 C  11 B + 0 e
 Electron capture: the capture by the nucleus
of an electron form the electron cloud
surrounding the nucleus
83 Rb + 0 e (orbital electron)  81 Kr
Section 2: Patterns of Nuclear Stability
 Neutron-to-Proton Ratio
Determines nuclear stability
By comparing neutron-to-proton ratios, you
can predict the type of radioactive decay
Predict the mode of (a) carbon-14
(a) Carbon’s atomic number is 6. 14-6=8
neutrons, making the neutron to proton ratio 1.3.
Carbon has a high neutron-to-proton ratio, so we
predict that it will decay by emitting a betaparticle.
14 C  0 e + 14 N
 Radioactive series: a series of nuclei breaking
apart until it becomes stable
Belt of stability
Section 3: Nuclear Transmutations
 Nuclear transmutation: a conversion of one
kind of nucleus to another
Brought about by bombarding nuclei with
either charged particles or neutrons
 Particle accelerators: increase the kinetic
energies of positively charged particles
Allows the particles to overcome their
electrostatic repulsion by the nucleus
 Transuranium elements: elements that follow
uranium in the periodic table
Section 4: Rates of Radioactive Decay
 Half-life: the time required for half of a sample of a
particular radioisotope to decay
 Rate = kN
k: decay constant
SI unit: becquerel (Bq) one nuclear disintegration per
Curie (Ci) corresponds to 3.7 x 1010 disintegration per
 The decay rate (activity) is proportional to the number
of radioactive nuclei and radioactive nuclei have
constant half-lives
Section 5: Detection of Radioactivity
 Geiger counter: a device that can detect and
measure radioactivity
 Scintillation counter: an instrument that is
used to detect and measure radiation by the
fluorescence it produces in a fluorescing
 Radiotracer: a radioisotope that can be used
to trace that path of an element in a chemical
Section 6: Energy Changes in Nuclear
 E = mc2 where E is energy, m is mass, and c
is the speed of light – 3.0 x 108 m/s
Small changes in mass mean large changes in
 mass defect: the difference between the
nucleus and its constituent nucleons
Energy + 42He  211p + 210n
 Nuclear binding energy: the energy required
to separate a nucleus into its individual
Section 6 Con’t
 Energy is produced when heavy nuclei split in
these two processes:
 Fission: splitting of a large nucleus into two
smaller ones.
 Fusion: the joining of two light nuclei two form
of more massive one.
Section 7: Nuclear Fisson
 Chain Reactions: A reaction in which the
neutrons produce in one fission cause further
fission reactions.
 Critical Mass: The mass necessary to
maintain this constant rate.
 Supercritical mass: A mass in excess of the
critical mass.
 In nuclear reactions, the fission is controlled
to generate a constant power.
Section 8: Nuclear Fusion
 Thermonuclear Reactions: Reactions in
which two nuclei are joined to form a more
massive one.
 High energies are needed to overcome the
repulsion between nuclei
The energy is achieved by high temperatures
Some reactions require temperatures up to
40,000,000 K