Chapter 19 Elements And Their Properties - C OF SCIENCE

9/5/2012Table of Contents1919Unit 5: Diversity of MatterChapter 19: Elements and Their Properties19.1: Metals19.2: Nonmetals19.3: Mixed GroupsMetals19.1Properties of MetalsMetals19.1 Metals usuallyhave commonproperties theyare goodconductors ofheat andelectricity, andall but one aresolid at roomtemperature. In theperiodictable,metals areelementsfound tothe left ofthe stairstep line.Metals19.1Properties of MetalsProperties of MetalsMetals19.1Ionic Bonding in Metals Metals also reflect light. This is a propertycalled luster. The atoms of metals generally have one tothree electrons in their outer energy levels. Metals are malleable (MAL yuh bul),which means they can be hammered orrolled into sheets. In chemical reactions, metals tend to giveup electrons easily because of the strengthof charge of the protons in the nucleus. Metals are also ductile, which means theycan be drawn into wires.1

9/5/2012Metals19.1Ionic Bonding in Metals When metals combine with nonmetals, theatoms of the metals tend to lose electrons tothe atoms of nonmetals, forming ionic bonds. Both metals andnonmetals becomemore chemicallystable when theyform ions.Metals19.1 In metallic bonding, positively chargedmetallic ions are surrounded by a cloud ofelectrons. Outer-level electronsare not held tightly tothe nucleus of an atom.Rather, the electronsmove freely amongmany positivelycharged ions.Metals19.1Metallic Bonding The idea of metallic bonding explains manyof the properties of metals. When a metal is hammered into a sheet ordrawn into a wire, it does not break becausethe ions are in layers that slide past oneanother without losing their attraction to theelectron cloud. Metals are also good conductors ofelectricity because the outer-level electronsare weakly held.Metals19.1The Alkali Metals The alkali metals are themost reactive of all themetals. They reactrapidly sometimesviolently with oxygen andwater. Alkali metals don’t occur innature in their elementalform and are stored insubstances that areunreactive, such as an oil.The Alkali Metals The elements in Group 1 of the periodictable are the alkali (AL kuh li) metals. Group 1 metals are shiny,malleable, and ductile. They are also goodconductors of heat andelectricity. However,they are softer than mostother metals.Metals19.1Metallic BondingMetals19.1The Alkali Metals Each atom of an alkali metal has oneelectron in its outer energy level. This electron is given up when an alkalimetal combines with another atom. As a result, the alkali metal becomes apositively charged ion in a compound suchas sodium chloride.2

9/5/2012Metals19.1The Alkali MetalsMetals19.1The Alkali Metals Alkali metals and their compounds havemany uses. The operation of some photocells dependsupon rubidium or cesium compounds. Doctors use lithium compounds to treatbipolar depression. Francium, the last element in Group 1, isextremely rare and radioactive. A radioactive element is one in which thenucleus breaks down and gives off particlesand energy.Metals19.1The Alkaline Earth Metals Each atom of analkaline earth metalhas two electrons inits outer energy level.Metals19.1The Alkaline Earth Metals The alkaline earth metals make up Group 2of the periodic table. These electrons are given up when analkaline earth metal combines with anonmetal. As a result, the alkaline earth metal becomesa positively charged ion in a compound suchas calcium fluoride, CaF2.Metals19.1Fireworks and Other Uses Magnesium metal isone of the metals usedto produce the brilliantwhite color infireworks. Compounds ofstrontium produce thebright red flashes.Metals19.1Fireworks and Other Uses Magnesium’s lightnessand strength account forits use in cars, planes,and spacecraft. Magnesium also is usedin compounds to makesuch things as householdladders, and baseball andsoftball bats.3

9/5/2012Metals19.1The Alkaline Earth Metalsand Your Body Calcium is seldomused as a free metal,but its compoundsare needed for life. Calcium phosphatein your bones helpsmake them strong.Metals19.1 The barium compound BaSO4 is used todiagnose some digestive disorders becauseit absorbs X-ray radiation well. Radium, the last element in Group 2, isradioactive and is found associated withuranium. It was once used to treat cancers.Metals19.1Transition Elements Transition elements are those elements inGroups 3 through 12 in the periodic table. They are called transition elements becausethey are considered to be elements intransition between Groups 1 and 2 andGroups 13 through 18.Metals19.1Iron, Cobalt, and Nickel The first elements in Groups 8, 9, and10 iron, cobalt, and nickel form aunique cluster of transition elements. These threesometimes are calledthe iron triad. All three elements areused in the process tocreate steel and othermetal mixtures.Transition Elements Transition elements are familiar becausethey often occur in nature as uncombinedelements. Transition elementsoften form coloredcompounds. Gems show brightlycolored compoundscontaining chromium.Metals19.1The Alkaline Earth Metalsand Your BodyMetals19.1Iron, Cobalt, and Nickel Iron the main component of steel is themost widely used of all metals. Nickel is added tosome metals to givethem strength.Click image to play movie4

9/5/2012Metals19.1Copper, Silver, and GoldMetals19.1Copper, Silver, and Gold Copper, silver, and gold the three elementsin Group 11 are so stable that they can befound as free elements in nature. Copper often is used in electrical wiringbecause of its superior ability to conductelectricity and its relatively low cost. These metals wereonce used widelyto make coins. Silver iodide and silver bromide breakdown when exposed to light, producingan image on paper. For this reason,they are known asthe coinage metals. Consequently, these compounds are usedto make photographic film and paper.Metals19.1Zinc, Cadmium, and Mercury Zinc, cadmium, and mercury are found inGroup 12 of the periodic table. Zinc combines with oxygen in the air toform a thin, protective coating of zinc oxideon its surface. Zinc and cadmiumoften are used to coat,or plate, other metalssuch as iron because ofthis protective quality.Metals19.1 Mercury is a silvery, liquid metal the onlymetal that is a liquid at room temperature. It is used in thermometers, thermostats,switches, and batteries. Mercury is poisonous and can accumulatein the body.Metals19.1The Inner Transition Metals The two rows of elements that seem to bedisconnected from the rest on the periodictable are called the inner transition elements.Zinc, Cadmium, and MercuryMetals19.1The Inner Transition Metals They are called this because like the transitionelements, they fit in the periodic tablebetween Groups 3 and 4 in periods 6 and 7, asshown.5

9/5/2012Metals19.1The Lanthanides The first row includes a series of elementswith atomic numbers of 58 to 71. These elements are called the lanthanideseries because they follow the elementlanthanum.Metals19.1The Actinides The second row of inner transition metalsincludes elements with atomic numbersranging from 90 to 103. These elements are called the actinide seriesbecause they follow the element actinium. All of the actinides are radioactiveand unstable. Thorium and uranium are the actinides foundin the Earth’s crust in usable quantities.Metals19.1Metals in the Crust Earth’s hardened outer layer, called thecrust, contains many compounds and a fewuncombined metals such as gold and copper. Most of the world’s platinum is found inSouth Africa.Metals19.1Ores: Minerals and Mixtures Metals in Earth’s crust that combined withother elements are found as ores. Most ores consist of ametal compound, ormineral, within amixture of clay or rock. The United States imports most of itschromium from South Africa, the Philippines,and Turkey.Metals19.1Ores: Minerals and Mixtures After an ore is mined from Earth’s crust,the rock is separated from the mineral. Then the mineral often is converted toanother physical form. This step usually involves heat and iscalled roasting.Section Check19.1Question 1What are common properties of metals?AnswerMetals are good conductors of heat andelectricity, reflect light, are malleable andductile, and, except for Mercury, are solid atroom temperature.6

9/5/2012Section Check19.1Section Check19.1Question 2AnswerWhich of these best describes electrons inmetallic bonding?The answer is B. In metallic bonding,positively charged metallic ions are surroundedby a cloud of electrons.A.B.C.D.electron acceptorelectron cloudelectron donorelectrons in fixed orbitsSection Check19.1Section Check19.1Question 3AnswerHow do alkaline earth metals differ from alkalimetals?Alkali metals have oneelectron in the outerenergy level of eachatom. Each atom ofalkaline earth metalshas two electrons in itsouter energy level.Nonmetals19.2Properties of NonmetalsNonmetals19.2Properties of Nonmetals Most of your body’s mass is made ofoxygen, carbon, hydrogen, and nitrogen. Phosphorus, sulfur, and chlorine are amongthese other elements found in your body. Calcium, ametal, and otherelements makeup theremaining fourpercent of yourbody’s mass. These elements are classified as nonmetals. Nonmetals are elements that usually aregases or brittle solids at room temperature.7

9/5/2012Nonmetals19.2Properties of NonmetalsNonmetals19.2Properties of Nonmetals Most nonmetals do not conduct heat orelectricity well, and generally they arenot shiny. The noble gases, Group 18, make up the onlygroup of elements that are all nonmetals. In the periodictable, allnonmetalsexcept hydrogenare found at theright of the stairstep line. Group 17 elements, except for astatine, arealso nonmetals.Nonmetals19.2Bonding in Nonmetals The electrons in most nonmetals are stronglyattracted to the nucleus of the atom. So, as agroup, nonmetals are poor conductors of heatand electricity. Most nonmetals can form ionic and covalentcompounds.Nonmetals19.2Bonding in Nonmetals When nonmetals gain electrons frommetals, the nonmetals become negativeions in ionic compounds. When bonded with other nonmetals, atomsof nonmetals usually share electrons to formcovalent compounds.Nonmetals19.2Hydrogen If you could count all the atoms in theuniverse, you would find that about 90percent of them are hydrogen.Nonmetals19.2Hydrogen A diatomic molecule consists of two atomsof the same element in a covalent bond. When water is brokendown into its elements,hydrogen becomes agas made up ofdiatomic molecules.8

9/5/2012Nonmetals19.2Nonmetals19.2Hydrogen Hydrogen is highly reactive. A hydrogen atom has a single electron,which the atom shares when it combineswith other nonmetals. Hydrogen can gain an electron when itcombines with alkali and alkalineearth metals. The compounds formed are hydrides. Halogen lightscontain smallamounts of bromineor iodine. These elements, aswell as fluorine,chlorine, and astatine,are called halogensand are in Group 17.Nonmetals19.2The HalogensNonmetals19.2The Halogens They are veryreactive in theirelemental form, andtheir compoundshave many uses.The Halogens Because an atom of a halogen has sevenelectrons in its outer energy level, only oneelectron is needed to complete this energylevel. If a halogen gains an electron from a metal,an ionic compound, called a salt is formed.Nonmetals19.2Nonmetals19.2The Halogens In the gaseous state,the halogens formreactive diatomiccovalent moleculesand can beidentified by theirdistinctive colors.Click image to play movie Chlorine is greenish yellow, bromine isreddish orange, and iodine is violet.The Halogens Fluorine is the most chemically active ofall elements. Hydrofluoric acid, amixture of hydrogenfluoride and water, isused to etch glass andto frost the innersurfaces of lightbulbsand is also used in thefabrication ofsemiconductors.9