    Atoms tend to attain stable electron configurations  All atoms like to be happy  (balanced or neutral) A nuclear reaction deals with reactions in which the nuclei of unstable isotopes gain stability by undergoing changes-radioisotopes These reactions are not effected by temperature, pressure, or a catalyst (speeds up or slows down reactions) These atoms cannot be slowed down, sped up or turned off

    The presence of too many or too few neutrons relative to the number of protons  Leads to an unstable nucleus  An unstable nucleus loses energy by emitting radiation- called radioactive decay Eventually, unstable radioisotopes of one element are transformed into stable isotopes of a different element Its spontaneous- does not require energy Creates different types of radiation

     Alpha particle- consists of helium nuclei that have been emitted (released) from a radioactive source.

  Atomic number decrease by 2 and mass by 4 Carry a positive charge Tend to not travel far (large mass and charge) Can be stopped by paper or skin In nuclear equations- written as 4 2 He or

α 238 92 U



234 90 Th +

4 2 He

    Beta particle- fast moving electrons formed by the decomposition of a neutron in an atom  In decomp. The new proton stays in nucleus, but releases an electron  Carry a negative charge Have MUCH less charge and mass than alpha particle More penetrating- can be stopped by aluminum foil or thin pieces of wood In nuclear equations 1 0 n  1 1 H + 0 -1 e

     high energy electromagnetic radiation given off by a radio isotope Often omitted along with alpha or beta particles No mass or electric charge Do NOT alter atomic number or mass number Nuclear equation=same as alpha or beta + gamma ray

     Behave essentially the same as gamma rays but origin is different They ARE NOT emitted during radioactive decay Are produced as excited electrons in certain metals when they lose energy Can pass easily through paper and wood Can’t be stopped completely  Several centimeters of lead or several meters of concrete

    A nucleus may be unstable for several reasons  Some nuclei have too MANY neutrons relative to the number of protons These nuclei decay by turning a neutron into a proton and by emitting a beta particle 1 0 n  1 1 H + 0 -1 e Other nuclei are unstable because of too FEW neutrons relative to the number of protons

   These become stable by converting a proton into a

neutron

 In this case an electron is captured! 59 28 Ni + 0 37 18 Ar + 0 -1 e  -1 e  59 27 Co How many protons? neutrons 37 17 Cl How many protons? Neutrons  Positrons  A particle with a mass of an electron but it has a POSITIVE charge  May be emitted as a proton changes into a neutron

   Examples   8 5 B  15 8 O  8 4 Be + 0 +1 e 15 7 N + 0 +1 e All nuclei with an atomic number greater than 83 are radioactive- too many neutrons or too many protons to be stable- they all undergo decay.

Most of them emit alpha particles- this helps increase the proton/neutron ratio

PARTICLE



Alpha



Beta



Gamma



Positron



proton

SYMBOL

     0 4 2

He

-1

e

1 0 0 γ 0 +1

e

1

H

 Time required for one-half of the nuclei of a radioisotope to decay into products     After one half life, half of the original sample will remain Every radioisotope has a unique half life Half life may be short- fraction of a second or long- billions of years Ex: Uranium-238 has an approximate half life of billions of years

 Imagine winning a $1000 prize but the conditions of the award require that half of the remainder of the prize is spent each month. After how many months would you be left with less then a $1? What is the half life of this prize?

 If the half life of a radioactive material is 8 yrs, how many years will it take for one half of the original amount of material to decay?

 Manganese-56 has a half life of 2.6hrs. What is the mass of manganese-56 in a 1.0mg sample of the isotope at the end of 10.4hrs?

 Start by figuring out how many half life's there will be.

  Transmutation- the conversion of an atom of one element to an atom of another element  Occurs during radioactive decay  Occurs when high energy particles bombard the nucleus Transuranium elements- elements on the periodic table with atomic numbers 92 and above.

 They all undergo transmutation   All are man made All are radioactive

     When nuclei are split apart because they have been bombarded with neutrons.

When fission occurs it creates smaller elements It also send more neutrons out that creates a chain reaction. Unleashes and ENOURMOUS amount of energy This is how nuclear power plants work  Occurs in nuclear reactors  Can be controlled

    When nuclei of smaller elements combine to produce nuclei of greater mass Hydrogen join to create helium Fusion only takes place in stars (our Sun)- it requires a HUGE amount of heat and pressure Fusion releases more energy then fission