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1、11.1 Outline of S-Block ElementsAlkali metals(IA):ns1 Li,Na,K,Rb,Cs,FrAlkaline earth Mmetals(IIA):ns2 Be,Mg,Ca,Sr,Ba,RaAll belong to active metalsIn this chapter,we focus on metallic activity,oxides,and basicity of hydroxides of S-block elements.CommonalitiesIA alkali metals:Li,Na,K,Rb,Cs,FrA alkali
2、ne earth metals:Be,Mg,Ca,Sr,Ba,Ra Their outermost electrons are both ns1 or ns2.Their sub-outer electrons have the same stable electronic structure as corresponding the inert gases,which can shield nuclear charges greatly.Therefore,I1 of alkali metals is the lowest among elements of the same period.
3、Atoms of alkali metals tend to lose one electron and become positively monovalent oxides without appearance of other oxidation states,so alkali metals are active.Alkali earth metals has one more nuclear charge than neighboring alkali metals.The nucleus is more attractive to two outermost s electrons
4、,so it is harder for alkaline earth metal to lose an electron than the corresponding alkali metal,and its I1 is larger than that of alkali metal.1.They tend to form MH and MH2 ionic compounds by directly reacting with hydrogen.2.They can form normal oxides,peroxides and superoxides with oxygen.3.The
5、y can easily react with water.(except for Be,Mg).4.They can react with non-metals to form corresponding compounds.Note：their activity is somewhat different Alkali metals and alkaline earth metals often combine with other elements to form the ionic compounds.But in some cases it still shows covalency
6、 to some extent.From top to bottom,atomic radius gradually increases,while ionization energy and electronegativity decrease.From top to bottom,metallic activity gradually increases.They can not exist in nature in form of elementary substance.Li Na K Rb CsBe MgCa SrBaMetal activity increasesMetal act
7、ivity increasesIA IIALi BeNa MgK Ca Rb SrCs BaAtomic radius,metallic activity and reducibility increase;while,ionization energy and electronegativity decrease.Atomic radius decrease;Metallic activity and reducibility decrease;Ionization energy and electronegativity increase.图片图片LiNaKRb CsBeMgCaSrBa1
8、1.2.Elementary substances of s-block elementsPhysical Properties:Metallic lusterLow densityLow hardness Low melting pointExcellent electrical and thermal conductivity图片Gc2-705-18.9The schematic illustrations of melting point change of elementary substances1.Physi-chemical Properties of elementary su
9、bstances These elementary substances have metallic luster,good conductivity and ductility;The alkali metal atom has only one valence electron and their atomic radius is bigger,therefore the metal bond is weak,and melting point,boiling point is low.The metal bond of alkaline earth metal is stronger,a
10、s well as melting point,boiling point,density and strength are also higher.Gc2-706-18.12They burn in the air to form corresponding oxides:Li2O,Na2O2,KO2,RbO2,CsO2,BeO,MgO,CaO,SrO,Ba2O2Li2ONa2O2KO21.they can react with oxygen,sulfur,nitrogen,halogen and form corresponding compounds.Chemical Pproperti
11、es of elementary substancesCombustion of Mg ribbon2.Reacting with water 2M+2H2O 2MOH+H2LiNaKCa2.Chemical properties Exception of Be and Mg,all other elementary substances easily react with water:2Na+2H2O =2NaOH +H2 Ca+2H2O =Ca(OH)2 +H2 Potassium reacts more strongly with water and burns than sodium;
12、Mg can react with cold water very slowly;Alkali and alkaline earth metals can also react with other non-metallic elementary substances and compounds.图图Cpp-262LiNaKCaSrBa3.Flame Reaction4.Reacting with liquid ammoniaAlbite:Potash feldspar:Carnallite:Alumstone:Spodumene:Beryl:Magnesite:Gypsum:Fluorite
13、:Celestine:Barite:Marble:2.Existence and preparation of s-block elementsExisting in form of mineralsTUPIANC-208Gc-717-18.23Beryl:Marble:Preparation methods(1)Na can be obtained by electrolysis of NaCl Anode：2Cl-=Cl2 +2e-Cathode：2Na+2e-=2Na Total reaction：2NaCl =2Na +Cl2(2)Thermal reduction method Ge
14、nerally,carbon or carbonide are used as reductants MgO(s)+C(s)=CO(g)+Mg(g)K2CO3+2C=3CO+2K 2KF+CaC2=CaF2+2K+2C(3)Metal replacement method at high temperature and low pressure KCl+Na=NaCl+K 2RbCl+Ca=CaCl2+2Rb 2CsAlO2+Mg=MgAl2O4+2Cs(4)Thermal decomposition method Cyanide,azide,and ferrocyanide can be decomposed by heat to form corresponding alkali metals.2MN3=2M+3N2 M=Na,K,Rb,Cs 4KCN=4K+4C+2N2