Chapter 3: Intro To the Periodic Table

History 1800’s- 60 known elements + their atomic masses 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.) 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 )

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 o Each period ends with a Noble Gas Each period ends with o a full s sublevel (___ v.e.-s) OR o full s & p sublevels (___ v.e.-s)

Using the Periodic Table, cont. Group Names o Group #1: Alkali Metals o Group #2: Alkaline Earth Metals o (Group #16: Chalcogens) o Group #17: Halogens o Group #18: Noble Gases

Physical States of the Elements The P. Table shows the state of the elements at room temperature. o Most elements are solid o Some elements are gas (most on right side of P Table. Only H is on left.) o 2 elements are liquid (Br & Hg)

3 Classes of the Elements: Common Properties MetalsNonmetalsMetalloids UsesVehicles, jewelry, coins, wires, computers Abundant in nature- fuels, living tissue, Computer chips, ExamplesNa, Ca, Ti, Cr, Fe, Cu, Ag, Zn, Pt, U H, He, C, N, O, F, I (most are gases) B, Si, Ge, As, Sb, Te, Po, At ColorSilvery luster (shine)Various Conductive (heat & electricity) VeryNoPoor to fair MalleableYesNo-Brittle, when solidOften brittle DuctileYesNo- “ “ “No Groups1*-12, most of 13, + inner transition elements H, 1 in Group 14 2 in Group 15 3 in Group 16 4 in Group 17 All of Group 18 Groups 13-17, only 1-2 elements in ea group # of v.e.-s1, 2, 3, Sn & Pb (4 v.e.- s), & Bi (5 v.e.-s) (4), (5), (6), 7 & 83-7 Behavior of v.e-sLoosely held-tend to lose them Tightly held-tend to share or gain them Moderately held- tend to share

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