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Topic 13 Periodicity

Topic 13 Periodicity . HL. Ionic or covalent bonding?. H-Cl. Na + Cl -. Cl-Cl. 13.1 Trends across third period; Chlorides. When you go  the number of valence electrons increase => increase the number of valence electrons to form bonds .

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Topic 13 Periodicity

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  1. Topic 13Periodicity HL

  2. Ionic or covalent bonding? H-Cl Na+Cl- Cl-Cl

  3. 13.1 Trends across third period; Chlorides • When you go  the number of valence electrons increase => increase the number of valence electrons to form bonds. • NaCl, MgCl2, AlCl3(Al2Cl6(g)), SiCl4, PCl5(PCl3 exist), (sulphur chlorides not required), (Cl2)

  4. Chlorides of metals (NaCl, MgCl2, AlCl3 ) • Ionicallybonded crystalline solids with high melting points. • Dissolves in water without a chemical reaction to its ions: NaCl (s) → Na+ (aq) + Cl- (aq) • Conduct electricity in melted or in aqueous solution.

  5. Chlorides of non-metals (SiCl4, PCl5 ) • Molecular covalent structure. • Weak forces between molecules => low melting and boiling points. • Don’t conduct electricity (no ions and no mobile charges).

  6. Reacts with water: Hydrolysis PCl3+ 3 H2O H3PO3 + 3 HCl Acidic solution (Phosphoric(III) acid, oxyacidof the element) H3PO3 + H2O H3O++ H2PO3- The oxyacid may also dissociate into acidic oxoniumions.

  7. In water the chlorides will conduct electricity; Cl- (aq). Chlorine, Cl2, if seen as Chlorine chloride, behaves in the same way: React with water in a hydrolysis reaction Cl2 + H2O  HCl + HClO Aluminium chloride reacts as a non-metal chloride due to small size and high charge. It’s very reactive with water: AlCl3 + H2O  Al2O3 + 6 HCl

  8. Oxides- across period 3 Trend: From basic to acidic character Base Acid Na2O, MgO, Al2O3, SiO2, P4O10, SO3(SO2), Cl2O7(Cl2O, Cl2O3, Cl2O5) Ionic Giant Covalent structure

  9. Left side- oxides are basic • Na2O + H2O  2 Na+ + 2 OH- • Magnesium hydroxide only weakly dissociated because of low solubility. • Reacts with acids (basic oxides): MgO(s) + 2 H+ Mg2+ + H2O

  10. In the centre- oxides are amphoteric • Both aluminium and silicon oxides are almost insoluble • Aluminium oxides have amphoteric properties; reacts with both base and acid Al2O3(s) + 6 H+ 2 Al3+ + 3 H2O Al2O3(s) + 2 OH- + 3 H2O  2 Al(OH)4-(aq) • Silicon dioxide can show weakly acidic properties; reacts with strong alkali to form silicates • Giant covalent lattices with high melting and boiling points

  11. To the right in period 3 • Molecular bonding: Gases, liquids or low melting points • The elements can often form 2 or more oxides with different state of oxidation. • Reacts with water to form acids. SO3(g) + H2O H2SO4 H2SO4 + H2O  H+ + HSO4- Cl2 + H2O  H+ +Cl- + HClO

  12. 13.2 First row d-block elements (ScZn)The transition elements • An element that contain an incomplete d level of electrons in one or more oxidation states • d-orbitalsstarts to fill up with electrons • They have some common characteristics (except Sc and Zn): • A variety of stable oxidation states • The ability to form ions • Coloured ions • Catalytic activity

  13. Oxidation states • The 4s and 3d orbitals are quite close in energy • The electrons in 4s orbitals can easily be lost • Gives stable state to the right of the d-block. To the left it’s a powerful reductant. (Ti2+ + water  Hydrogen) • Sc to Mn can loose all 4s and 3d electrons and stay stable. More to the right they become strong oxidants • Highest oxidation state usually occur as oxanions: E.g. dichromate (Cr2O72-), permanganate (MnO4-)

  14. Energy 3d 3d 4s 4s Mn2+ ion [Ar] 3d5 4s higherthan 3d Mn atom [Ar]4s23d5 4s lowerthan 3d

  15. Common oxidation states of the d-block elements

  16. All transition elements can show an oxidation number of +2 You should be familiar with Cr (+3, +6), Mn(+4, +7) Cu (+1,+2)

  17. In solution: Ligand • Ions of d-block elements have unfilled orbital's. These unfilled orbital's can attract a pair of electrons from an other compound = ligand. • The ligand must have free (non-bonding) electron pair that they can donate to the ion. • E.g. H2O, NH3, Cl-, CN-

  18. In solution: Complex ion • The ion and the ligand form a dative bond, co-ordinate bond(covalent) bond • The Ion + ligands = complex ion

  19. Examples of complex ions • Most complex ions have either six ligands arranged octahedrally around the central ion (often water or ammonia ligands) or four ligands arranged tetrahedrally (often chloride ligands) • [Cu(NH3)4]2+(forms when an excess of ammonia is added to Cu(II)-salt) • [Ag(NH3)2]+ • [Fe(H2O)6]3+ • [Fe(CN)6]3- • [CuCl4]2- • Complex formation can stabilise certain oxidation states and affect the solubility of the ion

  20. Complexes have often specific colours • In an isolated atom all d-orbital’s have the same energy. • The Ligandsin a complex ion affect the energy in the d-orbital’s. • The orbitals split up to two groups with different energy. The energy gap is in the visible region. • When light going through a transition metal solution energy is absorb when electrons are lifted from the lower level to the higher.

  21. http://www.chemguide.co.uk/inorganic/complexions/colour.html

  22. White light (all colours) hits Copper(II) salt and red and yellow light absorbs => blue-green colour. Sc3+ and Ti4+ : no electrons in d-orbitals => colourless Zn2+ : filled d-orbital => colourless

  23. Catalytic activity • Catalyst is a substance that speeds up a reaction without being consumed by it self. Reduce the activation energy. • Transition metals often have catalytic behaviour due to: • Ability to form complexes. Close contact. • Many oxidation states. Easy to lose or gain electrons in redox reactions.

  24. Homogeneous catalyst • In the same phase as the reactants • E.g. dissolved ion in water solution

  25. Heterogeneous catalyst • On the surface of the metal. E.g. • MnO2, Manganese(IV)oxide: 2 H2O2 2 H2O + O2 • Ni: Alkenes + hydrogen  Alkanes • Fe: Haber process, N2 + 3 H2 2 NH3 The worldwideammoniaproduction in 2004 was 109 million metrictonnes.[

  26. V2O5, vanadium(V)oxide: in the Contact process (manufacture sulphuric acid) 2 SO2(g) + O2(g)  2 SO3(g) SO3+ H2O  H2SO4 Sulphuric acid. 165 million tonnes, with an approximatevalue of US$8 billion. Principal usesincludeoreprocessing, fertilizermanufacturing, oilrefining, wastewaterprocessing, and chemicalsynthesis.

  27. Co in vitamin B12 Pd and Pd in catalyticconverters

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