number of protons and neutrons together
JUST the protons
calculation for AAM:
mass A (% of A) + mass B (% of B) and so on
when an element whose nucleus is unstable emits radiation on its own.
characteristics of natural
– nucleus becomes more unstable, as the neutron to proton ratio increases. Nucleus gives off radiation to stabilize itself
– cannot speed up or slow down
– all atoms with over 83 protons will automatically decay
when the opening of the nucleus releases a tremendous amount of energy that holds the nucleus together
normal chemical reactions include _________, not _____________________.
electrons, not protons and neutrons
When does a nuclear reaction occur?
when nuclei emits particles and/or rays
when does a chemical reaction occur?
when bonds are broken or formed
what happens to the atoms in nuclear reactions?
atoms are converted into atoms of another element
what happens to the atoms in chemical reactions?
remain unchanged but can be rearranged
what particles are involved in nuclear reactions?
protons, neutrons, and electrons
what particles are involved in chemical reactions?
only valence electrons
what are the energy changes in nuclear reactions?
what are the energy changes in chemical reactions?
what is the reaction rate affected by in a nuclear reaction?
what is the reaction rate affected by in a chemical reaction?
temperature, pressure, concentration
what is nuclear stability
the balance between electromagnetic forces and the strong force
what is strong force
force that holds the nucleus together, much stronger than the proton-proton repulsion force
low atomic numbers have a _______________ ratio.
1 to 1
larger atoms need a _____________ ratio
1.5 to 1
why do we need a bigger ratio?
as you add more protons, you have more repulsion and therefore need more neutrons to stabilize the nucleus
what is induced radioactivity?
it is forced to occur when a stable isotope is found to transmutate into an unstable one. This happens when the nucleus is hit with fast moving particles in order to create new elements
what is transmutation?
a change in the identity of a nucleus as a result of a change in the # of its protons
4 properties of radiation:
ionizes the air around it, glows, kills bacteria and small organisms, causes surroundings to rise in temp.
what is an alpha particle?
consists of two protons and two neutrons, a helium
what is a neutron particle?
1 over 0, n
what is a beta particle?
what is a positron
a positive electron
what is a gamma ray?
pure energy called a ray rather than a partice.
what is a proton particle?
referred to as hydrogen-1.
what two things must balance in the nuclear reaction?
atomic # AND mass #
beta emission (beta decay)
occurs when a neutron decomposes into a proton and an electron.
electron as the reactant, the nucleus draws in an inner shell electron, ratio below the band of stability
form in an unstable nucleus when a neutron changes into a proton and a positron
what is half life?
the time that it takes for 1/2 of a sample to decompose.
what is the formula for half life?
amount remaining= initial amount x 1/2 to the n
n= t/T, t= time elapsed and T= length of the half life
what is nuclear fission?
the splitting of atoms. One large atom splits into smaller fragments, neutrons and energy are released.
list the three steps for nuclear fission:
1) initiation- reaction if a single atom starts the chain (ex 235U and a neutron)
2) propagation- 236U fission releases neutrons that initiate other fissions
the combination of small nuclei. Light nuclei are combined at extremely high temps, forming heavy nuclei and giving off energy
why is fusion not as practicle as fission?
excessive heat cannot be contained, attempts at “cold” fusion have failed, “hot” fusion is difficult to contain