Download Nuclear Chemistry Test Topics

Things To Know For The Nuclear Chemistry Test
Transuranium elements are radioactive and produced by artificial transmutation and contain
more than 92 protons. The element uranium is the largest element that occurs naturally.
Transmutation occurs when one element is changed to another by changing the number of
protons (atomic number). Artificial transmutation occurs in particle accelerators.
Becquerel discovered that uranium gives off radiation by exposing photographic plates to
uranium salts. Marie and Pierre Curie discovered polonium and radium. Enrico Fermi was the
first to perform fission experiments.
Radiation consists of particles and energy being given off by unstable nuclei. It cannot be seen
or felt, but it is harmful to living things.
An isotope of an element differs in the number of neutrons it contains. To determine the mass
number of an atom, add the number of protons and the number of neutrons.
When there are more protons than neutrons in a nucleus, the nucleus becomes unstable. The
strong force cannot provide enough binding energy to hold the nucleus together, so the
nucleus will undergo radioactive decay. The series of steps the nucleus undergoes to become a
stable nucleus is called the decay series.
Alpha particles are the weakest form of radiation and cannot penetrate a sheet of paper or
clothing. The alpha particle is made up of a helium atom (2 protons and 2 neutrons). During
alpha decay the unstable nucleus loses 2 protons which decreases the atomic number by 2.
The unstable nucleus also loses 2 neutrons. The loss of 2 protons and 2 neutrons causes the
mass number of the atom to decrease by 4.
Beta particles are formed from the breakdown of a neutron into a proton and an electron. The
electron is the beta particle and is ejected from the nucleus along with large amounts of
energy. The gain of the proton from the breakdown of the neutron causes the atom’s atomic
number to increase by 1 while its mass number remains the same.
Gamma rays are electromagnetic waves that can penetrate several centimeters of lead. This is
the strongest type of radiation.
Remember, protons are positively charged and are attracted to negative charge while electrons
are negatively charged and attracted to positive charge. HINT: Think about a magnetic field
and how each type of radiation will react to that magnetic field.
The half-life of a radioactive element is the fixed rate of decay. It is equal to the time required
for ½ of the radioactive sample to decay to a stable state. Be able to perform half life
calculations.
Nuclear fission occurs when an unstable nucleus is bombarded by a neutron. This collision
causes the nucleus to break apart and release large amounts of energy. The pieces of the
broken nucleus bombard other unstable nuclei in the sample of material causing them to break
apart. This chain of one nucleus splitting and causing others to split is called a chain reaction.
At the end of fission stable nuclei will result and the energy released will be great! Uranium235 is commonly used in fission reactions. We use controlled fission to generate electricity in
nuclear power plants.
Nuclear fusion occurs when two smaller atoms are smashed together to form a larger atom.
Nuclear fusion also generates large amounts of energy, but occurs at too high a temperature
for man to use as an energy source. Fusion powers stars like our sun.
Know your vocabulary!
Know ways to detect radiation. Geiger counters are frequently used. Bubble chambers use a
superheated liquid to detect radioactivity.
Radioisotopes are used as chemical tracers because they have short half lives. They can be
used to heat homes, detect chemical leaks, or be used in medical applications. Radioisotopes
can be harmful, but their benefits sometimes outweigh the risks.
Protons and neutrons are located in the nucleus of an atom while the electrons orbit outside
the nucleus in specific areas called energy levels. The atomic number of an element tells how
many protons are in the nucleus of that element. The mass number is equal to the atomic
number plus the number of neutrons. Knowing this concept be able to calculate mass number,
atomic number or the number of neutrons.