Chapter 24 Nuclear Reaction and Their Applications
“24.1 Radioactive Decay and Nuclear Stability”
Nuclei: plural of nucleus (many nucleuses)
The great majority of nuclei are unstable. An unstable nucleus exhibits
it spontaneously decays by emitting radiation.
Protons (+) and neutrons (neutral), the elementary particles that make up the nucleus, are called
is a nucleus with specific numbers of the two
types of nucleons. Most elements occur in nature as a mixture of
, atoms w/ the same # of protons of the element but diff. numbers of neutrons. Each isotope
of an element is particular nuclide that we identify by its protons and neutrons.
X is the symbol for the particle, A-mass # (top) is mass number (sum of protons and neutrons), Z-atomic # is charge of particle (# of protons). The number of
neutrons (N) is mass # A -
atomic # Z.
nuclides can be written as element name followed by mass #, ex. Chlorine-35, or chlorine-37
Particle: atom, ion, or molecule
When a nuclide of one element decays, it emits radiation, and under most circumstances, changes into a nuclide of a diff. element. Three natural types of radioactive
are identical to helium-4 nuclei.
are high-speed electrons.
: are very high-energy photons (a quantum(indivisible amount) of electromagnetic radiation)
When a nuclide decays, it forms a nuclide of lower energy, and the excess energy is carried off by the emitted radiation and the recoiling nucleus. The reactant nuclide
(one that gets decayed) is called the
, the product nuclide is the
. Key principle for balancing nuclear reactions:
the total Z (charge, # of protons) and
the total A (sum of protons and neutrons) of the reactants equal those of the products:
Types of Decay:
involves loss of an alpha particle from a nucleus. For each alpha particle emitted by
the parent (reactant), A (atomic mass, protons +
neutrons) decreases by 4 and Z (atomic mass, # of protons) decreases by 2 in the daughter (product).
Every element beyond bismuth (Bi; Z=83) is radioactive
and exhibits alpha decay. So, alpha decay is the most common means for a heavy, unstable nucleus to become more stable.
Radium (Rn) undergoes alpha decay to yield radon (Rn; Z=86) :
222+4 ; Z: 88
general class of decay that includes 3 types:
emission, and electron capture.
involves the ejection of a
particle from the nucleus:
a neutron is converted into a proton, which remains in the nucleus, and a
again, total A and Z of reactants equals products