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Chapter 3: Intro To the Periodic Table History 1800’s- 60 known elements + their atomic masses 1829 - Döbereiner’s Triads (groups of 3) Some elements grouped in 3’s by their properties Physical properties of the middle element usual about ½ way between those of the other 2 elements. Ex: Halogen Triad: Cl, Br, I (see Table 3.1, p 87) Döbereiner Triads Halogen Triad: Cl, Br, I Alkali Triad: Li = 7 g Na = ? K = 39 g Coinage Metals Triad: Cu , Au, Ag History (cont.) 1869- Dmitri Mendeleev noticed that properties of elements repeated in an orderly way when organized by atomic mass. This is periodicity. He put them in order from lightest to heaviest (atomic mass) & grouped them when properties repeated themselves. (see Table 3.3 on p 90 of text) History, cont. Even though Mendeleev couldn’t identify Zn, Si, and Ca, he was able to predict their existence and their behavior! Modern Periodic Table Elements placed in order of increasing atomic number. Noble gases have been added Synthetic elements too Each period begins w/ a metal & ends w/ a noble gas (see p 92- 93) Using the Periodic Table (Review) Groups o Group # for Main Group Elements indicates the # of v.e-s o Elements in a group have similar chemical properties b/c the # of v.e-s is the same (AND VALENCE ELECTRONS DETERMINE CHEMICAL REACTIVITY!) Periods o Period # indicates the energy level of the v.e.-s Using the Periodic Table, cont. (New Info) Periods oEach period ends with a Noble Gas Each period ends with oa full s sublevel (___ v.e.-s) OR ofull s & p sublevels (___ v.e.-s) Using the Periodic Table, cont. Group Names oGroup #1: Alkali Metals oGroup #2: Alkaline Earth Metals o(Group #16: Chalcogens) oGroup #17: Halogens oGroup #18: Noble Gases Physical States of the Elements The P. Table shows the state of the elements at room temperature. oMost elements are solid oSome elements are gas (most on right side of P Table. Only H is on left.) o2 elements are liquid (Br & Hg) 3 Classes of the Elements: Common Properties Metals Nonmetals Metalloids Uses Vehicles, jewelry, coins, Abundant in nature- Computer chips, wires, computers fuels, living tissue, Examples Na, Ca, Ti, Cr, Fe, Cu, H, He, C, N, O, F, I B, Si, Ge, As, Sb, Te, Ag, Zn, Pt, U (most are gases) Po, At Color Silvery luster (shine) Various Conductive (heat Very No Poor to fair & electricity) Malleable Yes No-Brittle, when solid Often brittle Ductile Yes No- “ “ “ No Groups 1*-12, most of 13, + H, 1 in Group 14 Groups 13-17, only inner transition elements 2 in Group 15 1-2 elements in ea 3 in Group 16 group 4 in Group 17 All of Group 18 # of v.e.-s 1, 2, 3, Sn & Pb (4 v.e.- (4), (5), (6), 7 & 8 3-7 s), & Bi (5 v.e.-s) Metalloids Metalloids are often called semiconductors. They conduct heat & electricity, but poorly This is good in computers b/c they don’t overheat. Doping is used to make them better conductors. Metalloids & Doping Have an electron arrangement that keeps them from moving freely. Ex: each germanium atom (Ge) has 4 v.e.-s it shares with 4 neighboring Ge atoms. This creates a stable lattice, in which e-s are spaced evenly throughout the Ge, so they don’t move Metalloids & Doping “Doping”- If you place an occasional atom of another element, In or As, among the Ge atoms, you increase the movement of the e-s 2 Types of Doping n-type: creates a shortage of e-s, in some areas, so they move to try to even out the charges Indium has 3 v.e.-s, so in the lattice, there are “holes”- areas missing an e- 2 Types of Doping p type: creates an excess of e-s in some areas, so they move to try to even out charges
"Chapter 3 Intro To the Periodic Table"