Presentation on theme: "Chemistry came to be because people wanted to create gold from other elements. There is no “Chemical Reaction That will do this” Chemical reactions involve."— Presentation transcript:
Chemistry came to be because people wanted to create gold from other elements. There is no “Chemical Reaction That will do this” Chemical reactions involve the sharing or giving of electrons. We know elements because we know the # of protons they contain
Nuclear reactions do create new elements because they are reactions that involve the nucleus of an atom, called transmutation. Atoms of the same element can have the same # of protons but different #’s of neutrons. These elements are called Isotopes. The mass # of an element tells us the # of protons plus the # of neutrons C-14 and C-12 are isotopes of carbon what is the atomic #? How do these elements differ?
Most nuclei are stable, the ratio between protons and neutrons makes them stable. All elements with atomic # 83 or higher are unstable and break down by radioactive decay. These elements are called radioisotopes.
The nucleuses of Radioactive isotopes do not hold together well. The unstable nucleus will decay producing other elements as well as types of radiation. There are three types of radioactive decay: Alpha Beta gamma
In Alpha decay the nucleus of an unstable atom will releases a helium like particle. The atomic # of the original particle will decrease by 2 and the atomic mass will go down by 4. U-235 what will be the new mass the new atomic # and the new element formed after alpha decay? Stopped by paper not that dangerous
Stopped by Aluminum somewhat dangerous In beta decay the element releases a fast moving electron. The electron comes from the decomposition of a proton. The atomic # of the element increases by one and the atomic mass of the element remains the same.
Positron decay A positron is produced when a proton is converted to a neutron. Atomic # decreases by one Number of protons decreases by one Number of neutrons increases by one Mass # remains the same
In gamma decay high amounts of pure energy are released. The atoms atomic mass and the atoms atomic # does not change. This can only be stopped by concrete and aluminum very dangerous.
Artificial transmutation using alpha particles are achieved by using Cyclotons and synchrotrons Another type of transmutation uses naturally occurring nuetrons
Critical Mass Neutrons trigger more disintegrations
IsotopeHalf-Life 32 P14 days 35 S87 days 51 Cr27 days 125 I60 days 3H3H12.3 years 14 C5730 years Half life is the amount of time needed for one half of the radioactive material to break down. Example: How much of a 100 gram sample of P- 32 would be left after 28 days? How many days would it take for a 100 gram sample of I -125 to decompose to 25 grams? How old is a piece of wood if half of the carbon-14 remains?
Each gram of Carbon-14 emits about 15 disintegrations per minute. The half life for carbon-14 is 5730 years. So after 5730 years there will be only 7 disintegrations per minute. After about 4 half lives carbon- 14 is ineffective at dating things.
Radioactive isotopes are used to observe the chemical reactions within living things. These isotopes are called tracers.
Nuclear reactions are used to create heat and the heat is used to create steam which powers an electrical turbine.
Radioactive material is used to detect diseases, treat cancer and other diseases. Gamma rays are used to burn cancer Iodine-131 is used for the thyroid
Nuclear radiation can cause medical problems including mutations. One of the biggest concerns is nuclear power plants. After fuel rods are spent they still contain many decay products which are also dangerous. The question is what to do with the waste from these reactors?