Chem 104 Week 5 Caveats This week, we spend a lot of time going over the make-up of atoms.   In one part, we spend a lot of time looking at the nucleus (protons and neutrons) and how that affects the identity of the element and its mass number.  We then look at how the number of protons and electrons balance each other's (opposite) charges to see if that atom has a net ionic charge.  The key to understanding this section is to learn the relative masses and charges of the protons, neutrons and electrons. The main experiment for this week is the flame color experiment.  Cleanliness is very important for getting good results.  Do your best to make sure that you do not contaminate your testing wires.  For example, just a little bit of sodium contamination (even from your fingers) can disguise the true flame test color for another element.   In testing for flame colors, it works out best to place the wire low in the flame and near the outside of the flame.  If it's too close to the center of the inner flame, it won't get hot enough to show the color. Some compounds (e.g., potassium compounds) only hold their flame colors for a short time.  Pay attention to the early colors that you see. Pay particular attention to the Bohr model diagram on p. 12 of your notes when explaining flame colors. Pay attention to the modern energy level explanations on page 13.  Also, note the number of electrons per orbital (always 2), the number of orbitals per sublevel (i.e., s, p, d, f), and the total number of electrons per sublevel. Get familiar with doing calculations using Avogadro's number (6.02 x 1023 things/mole)