CHEM 1127Q Lecture Notes - Lecture 3: Atomic Mass, Bromine, Sodium Sulfide

• School: UConn
• Department: Chemistry
• Course: CHEM 1127Q
• Professor: Dr. Cady

Document Summary

Atomic mass = (fraction of isotope 1 x mass of isotope 1) + (fraction of isotope 2 x mass of isotope 2) + . Remember it"s the fraction of isotope 1. If you have the % you need to divide by 100 to get the fraction. We can now take these atoms and put them together into molecules. Molecular formula tells exactly of how many things there are. Empirical formula tells the ratios, gives the smallest number of everything. Metals on left side of table (usually positive), conductors. Metalloids along the borderline (bridge the gap), semiconductors. Nonmetals on right side of table (usually negative), not conductors. Groups 3-12 are called the transition metals. Group 18 = noble gases: inert, everything wants to be like a noble gas, charge = 0, don"t react. Group 17 = halogens: like to have -1 charge, very reactive. Group 1 = alkali metals: like to have +1 charge.