Nuclear Chemistry & Radioactive Nuclear Chemistry & Radioactive DecayDecay

Nuclear Chemistry DefinedChanges occurring WITHIN the nucleus

of an atomAtomic nuclei often emit particles or rays

Atoms of one element are often converted into atoms of another element

Can involve any of the subatomic particles

Big energy changes

Radiation & RadioactivityRadiation:Radiation:

the emission of nuclear particles by a radioactive substance

Radioisotope: Radioisotope: An isotope of an element with an

unstable nucleusInstability is caused by the imbalance of

protons and neutrons in the nucleus

Radioactive DecayThe process by which nuclear particles

are emitted from the nucleusIt reduces the amount of the substance

that originally existedIt is aimed at regaining stability in the

nucleus by restoring a proper balance between protons and neutrons

There are 4 main types of Radioactive Decay

1.1.Beta decay – Beta decay – “adds” a protona. A beta particle is essentially an electron

2.2.Alpha decay –Alpha decay – removes 2 protons & 2 neutrons

3.3.Positron emission –Positron emission – emits a positively charged beta particle

4.4.Electron capture – Electron capture – captures an electron to combine with a proton and make a neutron

Beta DecayNeutron releases a beta particleAtomic number increases by one.Mass number does not change

Radioactive Decay RatesHalf-Life:Half-Life:

The amount of time required for one-half of a radioisotope’s nuclei to decay into its products.

Half-Life Formula(s):Half-Life Formula(s):Amount remaining = (initial amount)(1/2)Amount remaining = (initial amount)(1/2)nn

Where n = the # of half-lives that have passed

ORORAmount remaining = (initial amount)(1/2)Amount remaining = (initial amount)(1/2)t/Tt/T

Where t = elapsed time and T = duration of half-life

Half-Life CalculationExample : Example : Iron-59 is used in medicine to

diagnose blood circulation disorders. The half-life of Iron-59 is 44.5 days. How much of a 2.000-mg sample will remain after 133.5 days?Known information:Known information:

Initial amount = Initial amount = 2.000-mg Elapsed time (t) = Elapsed time (t) = 133.5 days Half-life (T) = Half-life (T) = 44.5 days

Formula to use:Formula to use: Amount remaining = (initial amount)(1/2)t/T

Answer- .2500 mg

Nuclear Fission vs. Nuclear FusionNuclear Fission: the splitting of a nucleus into

smaller fragments accompanied by the release of neutrons and LARGE amounts of energy.

Nuclear Fission vs. Nuclear FusionNuclear Fusion: the process of combining

nuclei to produce a nucleus of greater mass, accompanied by HUGE amounts of energy.