1. Chemistry Chapter 4 Notes #3 (Sec 4)

2. Unstable Nuclei Nuclear Reactions Nuclear Reactions –Rxns that involve a change in the nucleus of an atom (most only involve e- changes) Radioactivity Radioactivity –When substances spontaneously emit radiation Radiation Radiation –Rays and particles emitted by radioactive material

3. Unstable Nuclei By emitting radiation atoms of one element can change into atoms of another element By emitting radiation atoms of one element can change into atoms of another element This happens because the nuclei is unstable This happens because the nuclei is unstable Atoms gain stability by losing energy (ex. Pencil falling over) Atoms gain stability by losing energy (ex. Pencil falling over)

4. Unstable Nuclei Unstable nuclei will lose energy by emitting radiation in a spontaneous process (so it doesn’t require energy) called radioactive decay Unstable nuclei will lose energy by emitting radiation in a spontaneous process (so it doesn’t require energy) called radioactive decay They undergo decay until they form stable non-radioactive atoms of a different element. They undergo decay until they form stable non-radioactive atoms of a different element.

5. Radiation-Alpha Positively charged alpha particles Positively charged alpha particles –Deflected toward a negative plate –Alpha particle – 2 p + and 2 n 0 –Symbol 4 2 He or α Nuclear Equation shows atomic # and mass # of the particles involved Nuclear Equation shows atomic # and mass # of the particles involved Ex. Alpha decay- Radium-226 into radon-222 Ex. Alpha decay- Radium-226 into radon-222

6. Radiation - Beta Negatively charged beta particles Negatively charged beta particles –Deflected toward a positive plate -with a -1 charge –symbol: 0 -1 ß Ex. Carbon-14 into Nitrogen-14 Ex. Carbon-14 into Nitrogen-14

7. Radiation - Gamma Not deflected by electric or magnetic fields Not deflected by electric or magnetic fields High energy radiation with no mass High energy radiation with no mass accompanies alpha and beta radiation accompanies alpha and beta radiation Denoted by the symbol: 0 0 У Denoted by the symbol: 0 0 У

8. Unstable Nuclei Atoms containing too many or too few neutrons are considered unstable Atoms containing too many or too few neutrons are considered unstable Stability is based on the ratio of neutrons to protons Stability is based on the ratio of neutrons to protons The END! The END!