Periodic Trends Section 8.6-8.8

Objectives Review the characteristics in metals, nonmetals, and metalloids Relate these characteristics to trends in atomic radius/ ionization energy/electron affinity

Key Terms Metallic character Nonmetallic character

Metals, Nonmetals, Metalloids

Metallic Character Degree to which an element exhibits the physical and chemical properties of a metal.

Metals Lustrous, malleable, ductile, good conductors All solids except liquid Hg

Metals LOW Ionization energy form positive ions easily Ionization energy decreases as metallic character increases

Ionic Compounds Form between metal and nonmetal Metal oxides are bases Metal oxide + H2O  metal hydroxide [7.9] Ionizes in water, freeing up the metal and O Metal oxide + acid  salt + H2O [7.12]

Nonmetals Dull, brittle, nonconductors (insulators). Gases: H, N, O, F, Cl, noble gases Liquid: Br KNOW PHYSICAL STATES OF ALL THE ELEMENTS!!

Nonmetals HIGH electron affinities  gain electrons and become negative ions

Molecular Compound Nonmetals with nonmetals Nonmetal oxides (CO2 or SO2) are acidic The more nonmetallic= more acidic the oxide Nonmetal oxide + H2O  acid [7.14] No dissociation (molecular) Nonmetal oxide + base  salt + H2O [7.16]

Metalloids Characteristics of both metals and nonmetals. Shiny, brittle All solids Semiconductors KNOW THEM!!

Overall Reactivity The most reactive metals are the largest since they are the best electron givers. The most reactive nonmetals are the smallest ones, the best electron takers.

Overall Reactivity

Homework 7.54 through 7.64 on page 294 EVENS only Exclude part (a) of 7.56 Exclude part (c) of 7.62 Exclude part (d) of 7.64

Group Trends Active Metals

Group Trends: Alkali Metals ns1 Very reactive Exist in nature only as compounds Soft metallic solids Na and K most abundant in Earth’s crust and biological systems Physical properties: Table 7.4 on p. 281

Alkali Metals React with… Hydrogen to form hydrides [7.17] Sulfur to form sulfides [7.18] H2O to form metal hydroxide and H2 [7.19] Oxygen Li forms metal oxide [7.20] Na forms metal peroxide [7.21] K, Rb, and Cs form superoxides [7.22]

The Alkaline Earth Metals ns2 Solids Harder and more dense than alkali Table 7.5 on p. 285 Less reactive than alkali Be and Mg are the least reactive

Alkaline Earth Metals Reactivity Be does not react with water or steam Mg does not react with water, reacts with steam Mg(s) + H2O (g)  MgO(s) +H2 (g) [7.23] All others react with water to form metal hydroxides and H2 [7.24]

The Alkaline Earth Metals Heavier alkaline earth ions give off characteristic colors when heated Ca = brick red Sr = crimson red Ba = green

The Alkaline Earth Metals Mg and Ca essential to growth and maintenance of the human body 99% of Ca in body is in skeletal system

Group Trends Selected Nonmetals

Hydrogen 1s1 Nonmetallic element in a class by itself- metallic inside the stars & Jovian planets Most abundant element in the universe Forms explosive mixtures with oxygen/halogens Reacts with metals to form hydrides [7.17] Loses it’s e- in H2O to form H+ ions

Chalcogens, ns2 np4 O, S, and Se are nonmetallic Te is a metalloid Po is a radioactive, rare metal Two allotropes of O (O2 and O3) O is a great oxidizer S has many allotropes S8 is the most common S reacts with almost every metal to form sulfides

Halogens, ns2,np5 Nonmetals Salt formers At is rare and radioactive All very reactive; not found in free form. Cl has the most industrial use Reactivity: F2 > Cl2 > Br2 > I2

Noble Gases, ns2,np6 . Each of these elements has a full octet Used to be the inert gases They are all unreactive Except XeF2, XeF4, XeF6 (Bartlett, 1962) Recently  KrF2; HArF (stable at low temp) He is commercially available-very expensive Ar is more common-less than 1% of the air

Homework 7.68-7.78 on page 295 EVENS only Not 7.68 b, c Not 7.78 a

Balanced Reactions 7.17 (true for any metal) 7.9 7.18 7.12 7.19 7.14* 7.20 7.21 7.22 7.23 7.24 7.9 7.12 7.14* 7.16* *Limited to any from the book, homework, or discussed in class