Nuclear Reactions

Elementary Particles  The only atomic particles that play a part in nuclear reactions are the protons and the neutrons; electrons do not play a part in nuclear reactions.  We use the following notation to describe the specific element we are considering in a nuclear reaction.  X represents the element, Z represents the atomic number (number of protons), and A represents the atomic mass number (the number of protons and neutrons) of the element.

Isotopes  For the nuclides below, determine the number of neutrons and protons.

Atomic Radii  Use the formula below in order to find the atomic radii of the following Nuclide.

Particle Masses  Nuclear masses are specified in unified atomic mass units or amu  The atomic mass of a neutron is u.  The atomic mass of a proton is u.  A neutral hydrogen atom, which has an electron and a proton but no neutron, has a mass of u.  We will use the mass of a neutral hydrogen in the place of the mass of a proton.  The mass of a nucleus is known to be u.  Compare this mass to the masses of the appropriate number of protons and neutrons combined.  What did you discover?  In the question above, you found that the actual mass was less than the mass of its constituent parts.  What do you think happened to the “missing mass?”

Binding Energy  The difference in masses discovered on the previous slide is known as the total binding energy of the nucleus.  This energy represents the amount of energy that must be put into the nucleus in order to break apart its protons and neutrons.  For a given nucleon, the total binding energy, E b, is  Find the amount of energy put into the following nuclide in order to break it apart.

Nuclides  This notation is very important because it allows us to represent different isotopes of an element X.  For a given atom, carbon for instance, nuclei are found that contain different numbers of neutrons even though they contain the same amount of protons.  Here are the symbols of some different isotopes of carbon.  They are all Carbon because they all have 6 protons; however, they have different numbers of neutrons.  These “different” carbons are known as Isotopes of each other.  The carbon to the left is known as “Carbon 12” because it has six neutrons and six protons.  The carbon to the right is known as “Carbon 16” and has six protons and ten neutrons.

Alpha Decay  Alpha decay is one of several types of nuclear decay.  In alpha decay a parent nucleus is broken apart to yield a daughter nucleus and an alpha particle.  The general equation for alpha decay is as follows.  An alpha particle is a neutral helium atom.

Q-Value  In alpha decay, the masses of the daughter nucleus and alpha particle combined are less than the mass of the parent nucleus.  The “missing mass” is converted into the kinetic energy of the alpha particle and the daughter nucleus.  This “missing mass” or released energy is known as the disintegration energy.  It is also known as the Q-value for the particular parent nucleus.  The equation used to determine the Q-value is  Find the daughter nuclide due to alpha decay and the Q-values or the nuclides below.

Beta Minus Decay  In Beta decay a parent nucleus is broken apart to yield a daughter nucleus and a Beta particle.  A Beta particle is either an electron (e-) or a positron (e+).  If an electron (also known as a  -) is emitted during the decay process, then the decay process is known as a “Beta minus decay.”  The general equation for beta minus decay is as follows.  The underlying reaction is the conversion of a neutron into a proton, electron, and an anti-neutrino. ProtonNeutron

Beta Minus Decay Calculate the KE for Beta Minus decay for KE max 0

Beta Plus Decay  If a Positron (also known as a  +) is emitted during the decay process, then the decay process is known as a “Beta plus decay.”  The general equation for beta plus decay is as follows.  The underlying reaction is the conversion of a proton into a neutron, positron, and a neutrino. Proton Neutron

Beta Plus Decay Calculate the KE for Beta Minus decay for KE max 0

Electron Capture  In electron capture, an orbital electron is captured by the nucleus, combines with a proton, and forms a neutron and a neutrino.  The general equation for electron capture is as follows.  The underlying equation for electron capture is the conversion of a proton and an electron into a neutron and a neutrino. Proton Neutron