Periodic TrendsGoals of the ExperimentMaterialsSafetyBackgroundSlide 6Slide 7Slide 8Background (Periodic table)Background (Periodic Trends)Slide 11Slide 12Lab 4Goals of the ExperimentMeasure bulk densities & calculate atomic densities of some transition metalsRelate density to atomic size (a periodic trend)MaterialsCr (25 to 30 g) ZCr = 24Mo (35 to 40 g) ZMo = 42W (55 to 60 g) ZW = 74Forceps or tongsWater10 ml graduated cylinderSafetyGlovesSafety goggles/glassesBackgroundDmitri Mendeleev arranged the Periodic Table in groups and in order of increasing atomic mass .BackgroundHenry Moseley rearranged the Periodic Table in order of increasing atomic number (Z).BackgroundAtomic number (Z)Number of electrons and protonsEx: Cr 24Atomic mass (M)Z + number of neutronsEx: MCr = 52 amuBackgroundAtomic Mass (M)Some of the mass of an element is converted into energy (nuclear binding ), E = mc2.Ex: Tungsten (Z = 74; MW = 184 amu). Actual mass (isotope) = 183.95093129 amu.1 amu = 1.66 x 10-27 kg.(Show calculation)Background (Periodic table)Property of an element depends on the location (family = vertical column; period = horizontal row).Background (Periodic Trends)Atomic RadiusIncreases from R to L; Increases from Top to Bottom(Show schematic view) Ionization Energy (IE) – Emin required to remove 1 e- from an atom/ion in its ground state and it correlates to reactivity of metals (exceptions).Increases from L to R; Decreases as you go down a familySmaller IE = more reactive the metalBackground (Periodic Trends)Electron affinity (EA) - ∆E associated with the addition of an electron to an atom/ion & it correlates to the reactivity of nonmetals (exceptions).Increases from L to R; Decreases as you go down a family.Larger EA = more reactive nonmetalBackground (Periodic Trends)Density also displays a periodic trend – atomic density increases from top to bottom but varies less significantly as one moves from left to right across a period.Bulk density depends on 3 properties:Mass of the atomsPacking arrangement (crystal structure – body centered, face centered, or simple cubic).Size of each