Periodicity 4. Chlorides of the 3 rd period. d-block elements

Transcription

1 Periodicity 4 Chlorides of the 3 rd period d-block elements

2 Period 3 oxides Last class, we talked about the trends we see as we move across the period 3 oxides. We saw that the melting points decrease as we go across left to right since the bonding gets progressively weaker We also saw that metal oxides are basic, aluminum oxide is amphoteric and non-metal oxides are acidic

3 Sample Question! Considering their structure and bonding, explain why molten Na 2 O conducts electricity whereas liquid SO 3 does not.

4 Chlorides of the 3 rd period The physical properties of the chloride are related to their structure in the same way as the oxides.

5 Chlorides of the 3 rd period

6 Chlorides of period 3 elements Formula NaCl MgCl 2 Al 2 Cl 6 SiCl 4 PCl 3 (PCl 5 ) S 2 Cl 2 Cl 2 State at Liquid Solid Solid Solid Liquid Liquid Gas 25 ⁰ C (solid) MP (⁰C) BP (⁰C) Conductivity Good Good Poor None None None None Bonding Ionic Simple covalent molecular Reaction with water Nature of solution Dissolve easily Weakly Neutral acidic Fumes of HCl produced acidic Some reaction with water

7 Reaction with Water When solid sodium chloride is placed in water, it dissociates into the sodium and the chloride ions. The ions are then surrounded by water molecules and become NaCl(s) + H 2 O (l) Na + (aq) + Cl - (aq) This solution is NEUTRAL!!! Similar reaction for magnesium chloride MgCl 2 (s) + H 2 O (l) Mg +2 (aq) + 2Cl - (aq)

8 Acidic chlorides 2AlCl 3(s) + 3H 2 O (l) Al 2 O 3(s) + 6HCl (aq) SiCl 4(l) +4H 2 O (l) Si(OH) 4(aq) + 4HCl (aq)! PCl 3(l) + 3H 2 O (l) H 3 PO 3(aq) + 3HCl (aq) Cl 2(g) + H 2 O (l) HClO (aq) + HCl (aq) These solutions are ACIDIC!!!

9 Sample Question! Write equations for the reactions of each of the following chlorides with water. chlorine, Cl 2 Cl 2 + H 2 O --> HClO + HCl silicon chloride, SiCl 4 SiCl 4 + H 2 O --> SiO 2 + 4HCl

10 In a public swimming pool, chlorine gas is used to produce hypochlorous acid, a powerful killer of bacteria and algae. Cl 2 + H 2 O --> HClO + HCl

11 Try it!

12 d-block elements Hydrated copper aluminum phosphate = Turquoise Manganese = used to promote immunity Iron = building your bridges Copper + Tin = Bronze

13 Transition element - an element that possesses an incomplete d sub-level in one or more of its oxidation states (when an ion)

14 Characteristics of Transition Elements Have multiple oxidation states Physical Properties: Have higher MP & are harder and denser than Alkali/Alkaline Earth metals Have catalytic properties Can form complex ions Can form coloured compounds

15 Variable Oxidation States The 3d and 4s sub-shells are similar in energy. When transition metals lose electrons, they lose the 4s electrons first. This is why ALL transition metals can show an oxidation state of +2 (lost 4s 2 e-) Some of the transition metals can form +3 or +4 ions as the ionization energies are low enough for up to two other electrons to be lost.

16 Example: Iron [Ar] 4s 2 3d 6 What types of ions can it form? Fe +2 Fe +3 [Ar] 3d 6 [Ar] 3d 5

17 Try! Oxidation numbers CrCl 3! chromium () chloride Cr 2 O 2! 7 dichromate () ion MnO 2! manganese () oxide MnO! 4 permanganate () ion Fe 2 O 3! iron () oxide Cu 2 O! copper () oxide

18 How did you do? CrCl 3! chromium (III) chloride Cr 2 O 2! 7 dichromate (VI) ion MnO 2! manganese (IV) oxide MnO! 4 permanganate (VII) ion Fe 2 O 3! iron (III) oxide Cu 2 O! copper (I) oxide

19 Physical Properties These properties make the d-block elements really useful: iron is used in building bridges, titanium is used in jet engines, chromium used in metalplating, copper is used in pipes and wires

20 Catalytic behaviour Catalysts increase reaction rate Many transition elements and their compounds are very efficient catalysts They are often used in industrial processes

21 Catalytic Converter

22 Explain the economic significance of the Contact or Haber Process

23 Formation of Complex Ions d-block ions are small and positive, they attract species that are rich in electrons. Ligands: neutral molecules or anions which contain a non-bonding pair of electrons (lone pair). Water is a common ligand Ammonia is a common ligand

24 Ligands These electron pairs can form co-ordinate covalent bonds with the metal ion to form complex ions. When the ligands change so does the colour of the complex The number of lone pairs bonded to the metal ion is known as the co-ordination number

25 Replacing Ligands

26 Write the formula [Cu(NH 3 ) 6 ] +2

27 Coloured Complexes In the free ion, the 5 d-orbitals have equal energy In complex ions, the d-orbitals are split into two distinct levels. The energy difference between the levels corresponds to a particular wavelength or frequency in the visible region of the spectrum

28 Coloured Complexes When lights falls on the complex, energy of a particular wavelength is absorbed and electrons are excited from the lower level to the higher level. If the d orbital is completely empty or completely full, no transitions within the d level can take place and the complexes are colourless.

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