Chapter 10

Radioactive nuclei
nuclei that undergo spontaneous changes and emit energy in the form of radiation
radioactive decay
a process in which an unstable nucleus changes energy state and in the process emits radiation
alpha particle
the particle that makes up alpha rays. It is identical to the helium nucleus and is composed of two protons and two neutrons
beta particle
the particle that make up beta rays. It is identical to an electron but is produced in the nucleus when a neutron is changed into a proton and an electron.
gamma rays
a high-energy ray that is like an x-ray but with a higher energy
an isotope of an element that emits nuclear radiation
daughter nuclei
the new nuclei produced when unstable nuclei undergo radioactive decay
a positively charged electron
electron capture
a mode of decay for some stable nuclei in which an electron from outside the nucleus is drawn into the nucleus, where it combines with a proton to form a neutron.
the time required for one half-life the unstable nuclei in a sample to undergo radioactive decay
radical or free radical
an electron-deficient particle that is very reactive
acute radiation syndrome
the condition associated with and following short-term exposure to intense radiation
inverse square law of radiation
a mathmatical way of saying that the intensity of radiation is inversely proportional to the square of the distance from the source
physical unit of radiation
a radiation measurement unit indicating the activity of the source of the radiation, for example the number of nuclear decays per minute
biological unit of radiation
a radiation measurement unit indicating the damage causedby radiation living tissues
a physical unit of radiation measurement corresponding to 3.7 x 10 to the 10th nuclear disintegrations per second
a physical unit of radiation measurement corresponding to one nuclear disintergration per second
a biological unit of radiation measuremnt
who discovered radioactivity
henri becquerel
what year was radioactivity discovered
how did henri becquerel discover radiation
photographic plate and rock containing uranium
what two people did most of the early work on radioactivity
pierre and marie curie
any change from one element into another
atomic number corresponds to what
the number of protons
mass number
number of protons plus number of neutrons
either a proton or a neutron
are isotopes always unstable
what isotopes of hydrogen are stable or unstable
1H and 2H are stable, 3H are unstable
which isotopes of carbon are stable and which are unstable
12C, and 13C are stable and 11C and 14C are unstable
what is the mass and charge of gamma rays
no mass or charge
beta particles
electrons from nucleus (not outer shell)
radioactive isotope
during an equation for nuclear reactions, the number of nucleons
stayes the same
the total number of nucleons in reactants in the same as the the total number of
nucleaons in the products
how many protons and neutrons are in an alpha particle
two of each
where do alpha particles come from
the nucleus
what is the charge on the alpha particles
plus 2
during positron emission a proton is converted into
a positron plus a neutron
during electron capture, an electron is sucked up by the nucleus and a
proton and a proton is converted into a neutron
definition of half-life
the time it takes for half of a radioactive sample to undergo decay
can you predict what the half life of a nuclide will be
no it must be determined experimentally
how are free radicals formed
radiation may knock electrons out of compounds, which form free radicals that are very reactive
which is more dangerous: long term or short term exposure to free radicals
long term
acute radiation syndrome is caused by
high doses of radiation in a short period of time (tissue rapidly destroyed)
radiation intensity varies with
distance squared
the farther away one is
the lower the intensity of radiation felt
rsoentgen are used with
x-rays or gamma rays (measures ionizing ability)
radiation absorbed dose
what does rentgen measure
ionizing ability
what do rads measure
energy transfered to the material
what do rems measure
health effects
three ways to measure radiation
geiger counter, film, scintillation counting
how do they measure radiation in the lab (the most accurate)?
scintillation counting
incorporate radioactive nuclides into biological molecules so can follow metabolilc processes
what do you want to be accurate when using radiation for therapeutic uses
the absporption to be very specific
what tracer do they use to follow photosynthesis
14 CO2
artificial transmutation
creation of a new isotope by bombardment of a material with particles
nuclear fission
a larder atom is split a part into smaller atoms
is a lot of energy given off during nuclear fission
what is the only natural element that will undergo fission
235 uranium
what happens to the nucleus during fission
it breaks apart and smaller atoms are created
nuclear fusion
elements melted together
where does fusion occur naturally
the sun