Nuclear Chemistry

Nuclear ChemistryRemember when we ionizeThe ELECTRONS only get moved to change the charge on an atom.WHY dont the PROTONS move when we ionize?When we change the number of protons, we change the element completely into another element!IsotopesSame elementSame number of protonsSame atomic numberSame number of electronsDifferent number of neutronsDifferent mass numberIsotope short-handC126Atomic symbolMass numberAtomic numberSo how many neutrons in this carbon?it is referred to as Carbon 12And this?C146is called Carbon 14There are 2 extra neutronsA note about Atomic Massatomic mass listed on the periodic table is the weighted average of mass of all the isotopes of an atom.Stabilityof isotopes is based on the ratio of the neutrons and protons in the atoms nucleus. although most nuclei are stable, some are unstable and spontaneously decay emitting radiation

Transmutationwhen the nucleus of an atom that converts it from one element to anotheri.e. we change the PROTONScan occur naturally or can be induced by the bombardment of the nucleus by high-energy particles. since the # of protons (atomic #) determines the atom, we CHANGE THE ELEMENT COMPLETELY.

Nuclear Reactionsinclude natural transmutationartificial transmutation, fission, and fusion.

Natural Transmutationdescribes nuclear changes due to natural radioactivity without any human intervention. Example: Radioactive Carbon-14 will decay to stable Nitrogen- 14 without any assistance.

Artificial TransmutationAn artificially induced nuclear rxn caused by the bombardment of a nucleus with subatomic particles (usually neutrons) or small nuclei (Hydrogen or Helium). In 1919 Ernest Rutherford bombarded nitrogen with alpha particles and converted it to hydrogen and oxygen, thus producing the first artificial transmutation of elements.

Rate of DecaySome radioactive atoms decay at a faster rate than others. The rate of decay is a chemical property of the atom and cannot be changed.

Drag Out YourReferencetablesHalf-LivesBecause it takes so long for all of an isotope to decay, scientists use the length of time it takes for one-half of the original amount to decay. This period is called the half life. Half life the time required for one half the mass of a radioactive sample to decay.

Half-Life Graph

Nothing changes Half LifeThe rate of decay for a radioactive sample is a set property of the sample. What happens to the half-life of a sample when you; Increase the Temperature? Nothing changes half-life Decrease the Temperature? Nothing changes half-life Increase the Surface Area? (i.e. grind it up) Nothing changes half-life Increase the Pressure? Nothing changes half-life

Nuclear ChemistryPart IITypes of DecayAlpha Decay emits an alpha particle. The new atom's atomic number is lowered by two and its atomic mass number is reduced by four.

Types of DecayBeta Decay emission of electrons from the nucleus The new atom's atomic number is raised by one and its atomic mass stays the same.

Types of DecayPositron Decay is the similar to Beta Decay except the particle released has a positive charge The new atom's atomic number is lowered by one and its atomic mass stays the same.

Types of DecayGamma Decay is the release of stored energy from the nucleus. No transmutation occurs. gamma decay often occurs with alpha and beta negative decay in a disintegration series.

Nuclear EnergyEnergy released in a nuclear reaction (fission or fusion) comes from the fractional amount of mass converted into energy. Nuclear changes convert matter into energy. From Einstein E=mC2 Energy released during nuclear reactions is much greater than the energy released during chemical reactions. There are benefits and risks associated with fission and fusion reactions.

Fission Rxnsoccur when a large nucleus splits into two or more smaller nuclei plus some by-products. By-products include free neutrons and photons (usually gamma rays). Fission releases substantial amounts of energy

FusionTwo or more smaller nuclei merge to form a larger nucleus, lots of energy and some by-productsNuclei of two isotopes of hydrogen, deuterium (D) and tritium (T) react to produce a Helium (He) nucleus and a neutron (n).

Uses of Radioisotopesused in medicineindustrial chemistryradioactive datingtracing chemical and biological processesindustrial measurementnuclear power,detection and treatment of diseases.

Geology UsesRadiometric dating- a process in which scientists attempt to determine the ratio of parent nuclei to daughter nuclei within a given sample of a rock or fossil. This ratio is then used to determine the absolute age of the rock or fossil. C-14 to C-12 ratio in dating organic things U-238 to Pb-206 ratio in dating crustal rocks

RisksThere are inherent risks associated with radioactivity and the use of radioactive isotopes. Risks can include biological exposure, long-term storage and disposal, and nuclear accidents.

Biological exposureAll radiation can cause damage to organisms. Most long-term damage is caused by the ionization of the atoms that make up the molecules in DNA. If the damaged DNA are found in egg or sperm cells, the effects may be passed on for many generations (mutations)

Long-term storage and disposalFission reactions in produce radioactive wastes. The wastes may have very long half-lives which make it difficult to dispose of them. Some solids and liquids need to be encased in special containers and permanently stored underground. Other materials are held until there radioactivity has lessened and are then diluted with other materials and released back into the environment.

Nuclear accidentsAn example of nuclear accident might be one in which a reactor core is damaged such as Three Mile Island (near Harrisburg PA) or Chernobyl, Ukraine and Fukishima, Japan.radiography accident where a worker drops the source into a river or sticks it in his pocket. Due to government and business secrecy, it is difficult to determine with certainty the extent of some events.

2012s Questions (handout)82 [1] Allow 1 credit. Acceptable responses include, but are not limited to:The nuclides used for fusion have smaller atomic masses than nuclides used for fission.The nuclides used in fission are many times more massive.Fusion particles are lighter.83 [1] Allow 1 credit for the correct number of protons and the correct number of neutrons for bothhydrogen nuclides.Example of a 1-credit response:

84 [1] Allow 1 credit for

85 [1] Allow 1 credit. Acceptable responses include, but are not limited to:Fusion produces more energy per gram of reactant.The fusion process produces less radioactive waste.The fusion reactant material is more readily available.