9/14 Opener What should I do if I need to go to the bathroom in Miss D’s class? Check to make sure no one is in the bathroom (only one person out at a time) Sign out with your name and time out Let Miss D know you are leaving the classroom Take the bathroom pass Upon return sign in with the time Failure to do this will result in loss of bathroom privileges

Nuclear Radiation and Transformation Chapter 25.1 and 25.2

Radioactivity In 1896 French chemist Becquerel, working with Marie and Pierre Curie discovered and named radioactivity Radiation is the penetrating rays and particles emitted by a radioactive source, like uranium Radioisotopes gain stability by undergoing changes accompanied by the release of large amounts of energy This process cannot be speed up, slowed down, or turned off. Unaffected by temperature, pressure, or catalysts An unstable nucleus releases energy by emitting radiation during the process of radioactive decay

Types of Radiation Alpha Radiation Beta Radiation Gamma Radiation A helium nuclei is emitted from a radioactive source, contains two protons, and two neutrons with a double positive charge 42He or α Ex. U Th + He Beta Radiation A neutron breaks into a proton, which stays in the nucleus, and a fast moving electron that is released 0-1e or β C N + e Gamma Radiation A high-energy photon emitted by a radioisotope, γ Have no mass or electrical charge Th Ra + He + Y 4 2 238 92 234 90 14 6 14 7 -1 230 90 226 88 4 2

Types of Radiation

Nuclear Stability and Decay There are 1500+ different nuclei and only 264 are stable The stability of a nucleus depends on neutron-to- proton ratio Stable nuclei are in a region called the band of stability The n-to-p ratio determines the type of decay A positron is a positive particle with the mass of an electron A proton changes to a neutron Mass is NOT conserved. A small amount is converted to energy.

Half-Life Half-Life is the time required for one-half of the nuclei of a radioisotope sample to decay to products After each half-life, half of the existing radioactive atoms have decayed into atoms of a new element

Transmutation Reactions Transmutation is the conversion of one element to an atom of another element This can occur by radioactive decay or by particles bombarding the nucleus of an atom Ex: uranium-238 undergoes 14 transmutations before reaching a stable isotope