Isotopes & Radioactive Decay

Electromagnetic Spectrum Radiation High energy rays and particles emitted by radioactive sources. (most invisible to human eyes) Includes: electromagnetic spectrum, alpha & beta particles. Electromagnetic Spectrum

Radioactivity The release of high-energy particles and rays from a substance due to changes in the nuclei of its atoms. Naturally occurring radiation found in our environment is called: “Natural Background Radiation” Radioactivity can be useful, such as in medical diagnoses and treatment (X-rays, Chemotherapy, etc.) and in generating electricity (Nuclear power plants)

Isotopes Atoms of the same element that have the… Same number of protons (same atomic number) Different number of neutrons Since the number of neutrons differs, the mass number also differs. Mass number = protons + neutrons Different isotopes of the same element all have: The same chemical symbol The same atomic number (# of protons) Different mass numbers

Representing Isotopes Use standard atomic notation Symbol + Atomic number + Mass number Also called “Nuclear Symbol” X Mass # Atomic # e.g.: Potassium has 3 naturally occurring isotopes. 39 K 40 K 41 K 19 19 19 Potassium-39 Potassium-40 Potassium-41 Protons 19 19 19 Neutrons 20 21 22 Electrons 19 19 19

Atomic Mass In nature, most elements are found as a mixture of isotopes. Potassium-39 Potassium-40 Potassium-41 93.26% 0.01% 6.73% Each banana has the same relative abundance of potassium isotopes The atomic mass of an element is the average of all the naturally occurring isotopes. Atomic mass = (.9326 x 39) + (.0001 x 40) + (.0673 x 41) = 39.1

Assignment Classwork: Homework: Practice Problems Q. 1-4 Page 291 “Isotopes” Worksheet Homework: “Isotopes and Ions” Worksheet