Periodic Trends Section

A Different Type of Grouping Broader way of classifying elements: Metals Nonmetals Metalloids or Semi-metals.

Metals, Nonmetals, Metalloids

There is a zig-zag or staircase line that divides the table. Metals are on the left of the line, in blue. Nonmetals are on the right of the line, in orange.

Metals, Nonmetals, Metalloids Elements that border the stair case, shown in purple are the metalloids or semi- metals. Aluminum is more metallic than not.

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

Metals Metals are lustrous (shiny), malleable, ductile, and are good conductors of heat and electricity. They are mostly solids at room temp. What is one exception?

Metals LOW Ionization energy  form positive ions easily cations

Nonmetals They are dull, brittle, nonconductors (insulators). Some are solid, but most are gases One is liquid…which is it?

Nonmetals HIGH electron affinities  gain electrons and become negative ions anions

Ionic Compounds Form between metal and nonmetal Metal oxides are bases React with acids to form salt and water

Metals lose e - s Nonmetals gain e - s A common feature of transition metals is that they often form cations of several different charges. Cr, for example, can be found as Cr 2+, Cr 3+ or Cr 6+. Ag and Zn are exceptions to this observation. Ag forms Ag + ions only, Zn forms Zn 2+ ions only

Molecular Compound Nonmetals combine with each other to form molecular compounds. Nonmetallic oxides, like CO 2 or SO 2 are acidic in aqueous solution.

Metalloids Characteristics of both metals and nonmetals. They are shiny but brittle Semiconductors

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

Group Trends: Alkali Metals Alkali Metals: ns 1 Soft metallic solids Na and K  most abundant in Earth’s crust and biological systems Physical properties on Table 7.4 on pg. 281

Group Trends: Alkali Metals Very reactive Exist in nature only as compounds React with hydrogen to form hydrides H- is a hydride ion And with sulfur to form sulfides

Group Trends: Active Metals React vigorously with H 2 O 2Na(s) + 2H 2 O(l) ---> H 2 (g) +2NaOH(aq) Very exothermic Reacts with oxygen 4Li + O 2 (g)  2Li 2 O (s) Metal oxide (only Li with O 2- ) 2Na + O 2 (g)  2Na 2 O 2 (s) Metal peroxides (all other alkali with O 2 2- ) K(s) + O 2 (g)  KO 2 (s) K, Rb, Cs form superoxides with O 2 - ion

Homework 7.54 through 7.60 on page 294 Black problems only

The Alkaline Earth Metals Solid at room temperature ns 2 Table 7.5 on page 285 Harder and more dense than alkali Less reactive than alkali Be and Mg are the least reactive

The Alkaline Earth Metals Be does not react with water or steam Mg does not react with water, but will with steam Mg(s) + H2O (g)  MgO(s) + H2 (g) All others react with water Ca(s) + 2H2O (l)  Ca(OH)2 (aq) + H2(g)

The Alkaline Earth Metals Tendency to lose two outer 2s electrons Form 2+ cation

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

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

Group Trends Selected Nonmetals

Hydrogen 1s 1 is a nonmetallic element in a class by itself- but is metallic inside the stars & Jovian planets the most abundant element in the universe. forms explosive mixtures with oxygen and halogens. Can react with metals to form hydrides. Can lose it’s e - in H 2 O to form H + ions.

Group 16 ns 2,np 4 Oxygen group O, S, and Se are nonmetallic Te is a metalloid Po is a radioactive, rare metal Two allotropes of Oxygen Oxygen is a great oxidizer Sulfur has many allotropes S 8 is the most common Sulfur reacts with almost every metal to form sulfides.

Group 17 ns 2,np 5 Nonmetallic Halogens = salt formers As is rare and radioactive They are all very reactive and not found in their free form. Cl has the most industrial use Reactivity: F 2 > Cl 2 > Br 2 > I 2 The smaller the atomic size the more reactive the nonmetallic atom

Group 18 ns 2,np 6 Noble Gases. Each of these elements has a full component of “p” electrons (except He). They are all unreactive Used to be called the inert gases He is commercially available, but is very expensive. Ar is more common as less than 1% of the air

Homework on page 295 Black problems only