Group IV Elements <ul><li>Section 3.4: Discuss the trends in </li></ul><ul><li>Bonding </li></ul><ul><li>Acid/ Base Charac...
The Group IV Elements <ul><li>Carbon – Silicon – Germanium – Tin - Lead </li></ul><ul><li>All elements in this group has 4...
(i) Bonding <ul><li>We are all familiar with the fact that C is a non-metal and Pb is a metal. </li></ul><ul><li>The metal...
<ul><li>Carbon and silicon are non metals </li></ul><ul><li>Germanium is a metalloid, i.e. has an intermediate character. ...
<ul><li>C, Si, Ge: forms covalent compounds with other elements, usually 4-valent. </li></ul><ul><li>Sn: covalent +4 and i...
(ii) Acid/Base Nature <ul><li>As you go down group 4 of the periodic table, the acidity of the oxides decrease with increa...
<ul><li>Most elements in group 4 are able to form either a +2 ion or a +4 ion. </li></ul><ul><li>The oxides of oxidation s...
<ul><li>Carbon Monoxide, CO </li></ul><ul><li>- slightly acidic </li></ul><ul><li>- does not react with water but will rea...
<ul><li>Carbon and Silica Dioxide CO 2  , SO 2 </li></ul><ul><li>- weakly acidic </li></ul><ul><li>CO 2   reacts with wate...
<ul><li>CO 2  reacts with the base NaOH in the cold to give either sodium carbonate or hydrocarbonate (depending on the pr...
<ul><li>SO 2  does not react with water, since it is difficult to break up its covalent structure. </li></ul><ul><li>SO 2 ...
<ul><li>Monoxides of Ge, Sn and Pb </li></ul><ul><li>- all amphoteric, they show both basic and acidic properties. </li></...
<ul><li>Lead (II) chloride is fairly insoluble in water and instead of getting a solution, it would form an insoluble laye...
<ul><li>- Acidic Nature of Monoxides </li></ul><ul><li>The monoxides of Ge, Sn and Pb all react with bases like NaOH. </li...
<ul><li>Dioxides of Ge, Sn and Pb </li></ul><ul><li>- amphoteric </li></ul><ul><li>Basic Nature of the Dioxides </li></ul>...
<ul><li>They even react with excess Cl -  ions in the HCl to give complexes such as XCl 6 2- </li></ul><ul><li>XCl 4  + 2C...
<ul><li>Acidic Nature of the Dioxides </li></ul><ul><li>The dioxides react with hot conc. NaOH solution to give soluble co...
<ul><li>Summary </li></ul><ul><li>CO 2 : dissolves in water to form a weak acid </li></ul><ul><li>CO :  reacts with molen ...
(iii) Thermal Stability of the Oxides <ul><li>First it is important to acknowledge that the oxides of oxidation state IV i...
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3.4

  1. 1. Group IV Elements <ul><li>Section 3.4: Discuss the trends in </li></ul><ul><li>Bonding </li></ul><ul><li>Acid/ Base Character </li></ul><ul><li>Thermal stability of the oxides of oxidation states II and IV </li></ul>
  2. 2. The Group IV Elements <ul><li>Carbon – Silicon – Germanium – Tin - Lead </li></ul><ul><li>All elements in this group has 4 valent electrons </li></ul><ul><li>However, as atomic number increases along this group there is a considerable change in character of the elements. </li></ul><ul><li>Si </li></ul>C Ge Sn Pb
  3. 3. (i) Bonding <ul><li>We are all familiar with the fact that C is a non-metal and Pb is a metal. </li></ul><ul><li>The metallic (electropositive) character of the elements increase as atomic number increases. </li></ul><ul><li>The non-metallic (electronegative) character decreases as atomic number increases along group 4. </li></ul>
  4. 4. <ul><li>Carbon and silicon are non metals </li></ul><ul><li>Germanium is a metalloid, i.e. has an intermediate character. </li></ul><ul><li>Tin and lead show typical metallic properties. </li></ul><ul><li>Carbon, silicon and germanium are giant molecular structures </li></ul><ul><li>Tin and lead are metallic structures. </li></ul>
  5. 5. <ul><li>C, Si, Ge: forms covalent compounds with other elements, usually 4-valent. </li></ul><ul><li>Sn: covalent +4 and ionic +2 states are formed with almost equal ease </li></ul><ul><li>Pb: forms mainly ionic compounds in it +2 state and covalent compound sin its +4 state </li></ul>
  6. 6. (ii) Acid/Base Nature <ul><li>As you go down group 4 of the periodic table, the acidity of the oxides decrease with increasing atomic number. </li></ul><ul><li>The oxides of the elements are acidic. Towards the bottom of the group, the oxides become more basic, but never loses their acidity. </li></ul><ul><li>They are therefore said to be amphoteric. </li></ul>
  7. 7. <ul><li>Most elements in group 4 are able to form either a +2 ion or a +4 ion. </li></ul><ul><li>The oxides of oxidation state II are monoxides while those of oxidation states IV are dioxides. </li></ul>
  8. 8. <ul><li>Carbon Monoxide, CO </li></ul><ul><li>- slightly acidic </li></ul><ul><li>- does not react with water but will react with hot conc’n NaOH to give a solution HCOONa. </li></ul><ul><li>NaOH + CO HCOONa </li></ul><ul><li>No oxide of oxidation state II exist for silicon. </li></ul>
  9. 9. <ul><li>Carbon and Silica Dioxide CO 2 , SO 2 </li></ul><ul><li>- weakly acidic </li></ul><ul><li>CO 2 reacts with water to produce H+ ions and a HCO 3 </li></ul><ul><li>H2O (l) + CO 2(g) H + (aq) + HCO 3 - (aq) </li></ul><ul><li>The position of eq’brm is well to the left hand side . </li></ul>
  10. 10. <ul><li>CO 2 reacts with the base NaOH in the cold to give either sodium carbonate or hydrocarbonate (depending on the proportions) </li></ul><ul><li>2NaOH + CO 2 Na 2 CO 3 + H 2 O </li></ul><ul><li>NaOH + CO 2 NaHCO 3 </li></ul>
  11. 11. <ul><li>SO 2 does not react with water, since it is difficult to break up its covalent structure. </li></ul><ul><li>SO 2 reacts with hot, concentrated NaOH solution. Sodium silicate solution is formed. </li></ul><ul><li>2NaOH + SiO 2 Na 2 SiO 3 + H 2 O </li></ul>
  12. 12. <ul><li>Monoxides of Ge, Sn and Pb </li></ul><ul><li>- all amphoteric, they show both basic and acidic properties. </li></ul><ul><li>- Basic Nature of the oxides </li></ul><ul><li>These oxides react to form salts </li></ul><ul><li>E.g. Rxn with concentrated HCl </li></ul><ul><li>XO (s) + 2HCl (aq) XCl (aq) + H2O (l) , where X can be Ge, Sn or Pb. </li></ul>
  13. 13. <ul><li>Lead (II) chloride is fairly insoluble in water and instead of getting a solution, it would form an insoluble layer over the lead (II) oxide, if you were using dilute HCl – stopping the rxn from going on. </li></ul><ul><li>The large excess of Cl - ions in the conc’n acid react with the PbCl 2 to produce soluble complexes such as PbCl 4 2- </li></ul><ul><li>PbCl 2 (s) + 2Cl - (aq) PbCl 4 2- (aq) </li></ul>
  14. 14. <ul><li>- Acidic Nature of Monoxides </li></ul><ul><li>The monoxides of Ge, Sn and Pb all react with bases like NaOH. </li></ul><ul><li>XO (s) + 2OH - aq) XO 2 2- (aq) + H 2 O (l) </li></ul>
  15. 15. <ul><li>Dioxides of Ge, Sn and Pb </li></ul><ul><li>- amphoteric </li></ul><ul><li>Basic Nature of the Dioxides </li></ul><ul><li>The dioxides react with the conc. HCl first to give compounds of the type XCl 4 </li></ul><ul><li>XO 2 + 4HCl XCl 4 + 2H 2 O </li></ul>
  16. 16. <ul><li>They even react with excess Cl - ions in the HCl to give complexes such as XCl 6 2- </li></ul><ul><li>XCl 4 + 2Cl - XCl 6 2- </li></ul><ul><li>PbO 2 reacts with cold HCl. In hot or warm HCl, the lead (IV) chloride decomposes to give lead (II) chloride and chlorine gas. </li></ul>
  17. 17. <ul><li>Acidic Nature of the Dioxides </li></ul><ul><li>The dioxides react with hot conc. NaOH solution to give soluble complexes of the form [X(OH)6]2- </li></ul><ul><li>XO 2(s) + 2OH - (aq) + 2H 2 O (l) [X(OH) 6 ] 2- </li></ul>
  18. 18. <ul><li>Summary </li></ul><ul><li>CO 2 : dissolves in water to form a weak acid </li></ul><ul><li>CO : reacts with molen NaOH sodium methanoate </li></ul><ul><li>SiO 2 : reacts with a molten base a silicate </li></ul><ul><li>SnO 2 / SnO : react with dilute acid Sn4+ and Sn2+ salts and react with a molten base or conc aq. alkali to form a stannate (IV) or a stannate (II) </li></ul><ul><li>PbO 2 /PbO : react with dilute acids Pb (IV) compounds and Pb2+ salts and with a molten base or conc aq. alkali to form a plumbate (IV) or a plumbate (II). PbO is more basic than PbO 2 . </li></ul><ul><li>Pg 425 Ramsden </li></ul>
  19. 19. (iii) Thermal Stability of the Oxides <ul><li>First it is important to acknowledge that the oxides of oxidation state IV is more stable than those of oxd’n state II at the top of the group. </li></ul><ul><li>As atomic number increase going down the group, +2 oxd’n state becomes more stable than the +4 oxd’n state. </li></ul>

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