Name: _________KEY___________
Hour: ____ Date: ___________
Chemistry: Vocabulary – Nuclear Chemistry
Directions: Define each of the following terms. For some of the terms, you may need to consult sources other
than your textbook.
1. alpha decay
vs.
beta decay
a helium nucleus is ejected from the
atom’s nucleus; the atomic number
drops by two
a fast-moving electron is ejected from the
atom’s nucleus; the atomic number
increases by one
2. band (or belt) of stability
a graphical representation of the stable nuclides, with the atomic number (Z) on the
horizontal axis and the number of neutrons (A – Z) on the vertical axis
3. breeder reactor
a nuclear reactor that generates more radioactive fuel than it consumes, by converting
nonfissionable U-238 into fissionable Pu-239
4. chain reaction
and
critical mass
a reaction that will sustain itself, without
any further input from external sources
5. control rods
vs.
the amount of fissionable material one
needs to amass in a single place in order
to induce a nuclear chain reaction
moderator
in a nuclear reactor, these absorb neutrons
and thus control the rate of the reaction
the substance in a nuclear reactor that
slows down the neutrons so that they
will induce fusion
6. electron capture
when an electron in an inner energy level is captured by the nucleus; the atomic number
decreases by one
7. fission
vs.
the splitting of heavy atomic nuclei
(like U or Pu) into less massive fragments
fusion
the joining/fusing of light atomic nuclei
(like H) to form more massive nuclei
(like He)
8. gamma radiation
high-energy electromagnetic radiation emitted from an unstable nucleus, due to the nucleons
rearranging themselves into a more stable arrangement; gamma emission often accompanies
other radioactive emissions, such as  or  emission
9. half-life
the amount of time required for one-half of a radioactive sample to decay into nonradioactive
(i.e., stable) matter
HC-V-MMX
10. isotopes
vs.
different varieties of an element’s atoms;
specifically, ones that vary in terms of
their numbers of neutrons
11. mass defect
and
the difference between what a nuclide’s
nucleons would weigh by themselves (more)
compared to what they weigh when they are
bound together in the nucleus
12. nucleon
and
a generic term for a particle in the
nucleus; i.e., a proton or a neutron
13. nuclide
radioisotopes
the isotopes of a given element that
are radioactive
nuclear binding energy
the energy that holds the nucleons
to each other in the nucleus; it is found
by using the mass defect in the equation
E = m c2
mass number
for a nuclide, the sum of all of the
nucleons in the atom’s nucleus
vs.
a nucleus with a specified number of
protons and neutrons
radionuclide
a nuclide that is radioactive and that
therefore emits energy and/or particles
14. positron
a particle having the same mass as an electron, but having a positive charge rather than
negative; a positron is the antimatter particle of an electron; its name comes from a merging
of the terms “positive” and “electron”
15. radioactive series
a sequence of nuclear transmutations a species undergoes as it progresses from an unstable
nucleus to a final, stable nucleus; there are three radioactive series, ending at Pb-206, Pb-207,
and Pb-208
16. radioactivity
vs.
the energy and/or particles emitted by
an unstable nucleus
nuclear transmutation
the changing of one type of atom into
another type of atom; this requires a
nuclear reaction
17. shell model of the nucleus
the theory that nucleons occupy various energy levels within the nucleus; analogous to
how electrons occupy various energy levels in the atom
HC-V-MMX