Chapter 2Isotopes:- Atoms with the same atomic number but different mass numbers- All atoms of same element have same number of protonso Can have different number of neutrons- Hydrogeno Protium (or just hydrogen) – 1 protono Deutrerium – 1 neutrono Tritium – 1 proton and 2 neutrons Isotope Abundance:- Percent abundance = (number of atoms of given isotope/total number of atoms of all isotopes of that element) x 100Atomic weight - Average mass of a representative sample- Atomic weight= [(% abundance isotope 1/100) x (mass of isotope 1)] + [(% abundance isotope 2/100) x (mass of isotope 2)] + …- The atomic weight of an element is always closer to the mass of the most abundant isotopePeriodic Table- Metalloids – element that has some physical characteristics of metal but somechemical characteristics of nonmetalso B, Si, Ge, As Sb and Te- Group 1Ao Alkali metalso Solid at room temperatureo All reactiveo Only found in nature combined in compounds (NaCl, H2O)- Group 2Ao Alkaline earth metalso React with water to form alkaline solutions- Group 3Ao Aluminum (most abundant metal), gallium, indium and thallium are metalso Boron is metalloid- Group 4Ao Carbon – nonmetalo Silicon and germanium – metalloidso Tin and lead – metalso More variation in propertieso Form compounds wit analogous formulas (CO2, SiO2, GeO2, PbO2)o Allotropes – particular elements can exist in several different and distinct forms each having own properties- Group 5Ao Nonmentals – nitrogen and phosphorouso Metalloids –As and Sbo Metal – Bio Form analogous compounds (N2O5,