AP Day 20

After reviewing Thomson & Millikan's work to characterize the electron, and Chadwick's discovery of the neutron, we discussed nuclide symbols (element symbols in the center with numbers in each of the four corners of the symbol) and their make-up.  We completed guided practice in determining protons, neutrons and electrons for both isotopes & ions that were given, as well as determining the isotope or ion when given the total number of protons, neutrons and electrons.
We discussed how Dalton's assertion that all atoms of the same element are exactly alike and how scientists determined this to be incorrect with the discovery of isotopes (atoms of the same element that have different masses, due to different numbers of neutrons in the nucleus).  Students used the Isotopes & Atomic Mass PhET simulation (see below) to explore the concepts of nuclear stability and the p/n ratio in the nucleus, as well as the role that isotopic abundance plays in determining the average atomic mass (the mass value found on the periodic table) of a given element.