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- Transition metals and refractory metals (Cr, Mo, W).
- Wide oxidation states.
- Include:
Chromium (Cr) Molybdenum (Mo) Tungsten (W)
and Seaborgium (Sg).
GROUP VIB - INTRODUCTION1) Overview:
GROUP VIB - INTRODUCTION1) Overview:
Tungsten:
• Lowest coefficient of thermal expansion
• High melting point
• Strength of tungsten are due to strong covalent bonds
Highest meltingpoint
GROUP VIB - INTRODUCTION2) Natural resouces:
Chromium
Crocoite (PbCrO4) Chromite (FeCr2O4)
2) Natural resouces:
GROUP VIB - INTRODUCTION
Molybdenum
Molybdenum:
Wulfenite ( PbMoO4 )
Powellite (CaMoO4 )
Molybdenite ( MoS2)2
2) Natural resouces:
GROUP VIB - INTRODUCTION
Wolframite (Fe,Mn)WO4
Scheelite (CaWO4),
Hübnerite (MnWO4).
Tungsten :
GROUP VIB – PHYSICAL PROPERTIES
• White metal silver shiny
• Heavy metals
• Good electrical conductivity
Thermal conductivity
• Highest melting point
GROUP VIB – PHYSICAL PROPERTIES
Chromium Molybdenum Tungsten
Atomic number 24 42 74
Electron configuration [Ar] 3d54s1 [Kr] 4d55s1 [Xe] 4f145d46s2
Melting point 1907°C 2622°C 3414°C
Boiling point 2671°C 4639°C 5555°C
Relative atomic mass 51.996 95.95 183.84
Key isotopes 52Cr, 53Cr and 54Cr 95Mo, 96Mo, 98Mo 182W, 184W, 186W
GROUP VIB – CHEMICAL PROPERTIES
• Sustained with air, moisture and carbon dioxide
• Reacts with oxygen at high temperatures
4Cr (s) + 3O2 (g) → 2Cr2O3 (s) ( in 300oC, ∆Ho = -1141 kJ/mol )
2Mo (s) + 3O2 (g) → 2MoO3 (s) ( in 600oC, ∆Ho = -745 kJ/mol )
2W (s) + 3O2 (g) → 2WO3 (s) ( in 600oC, ∆Ho = -842 kJ/mol )
GROUP VIB – CHEMICAL PROPERTIES
• Reacts with fluorine gas at room temperature
2Cr(s) + 5F2(g) → 2CrF5(s) [red]
• Chromium reacts with fluorine, F2, at 400°C and 200-300 atm
Cr(s) + 3F2(g) → CrF6(s) [yellow]
2Cr(s) + 3F2(g) → 2CrF3(s) [green]
2Cr(s) + 3Cl2(g) → 2CrCl3(s) [red-violet]
2Cr(s) + 3Br2(g) → 2CrBr3(s) [very dark green]
2Cr(s) + 3I2(g) → 2CrI3(s) [very dark green]
GROUP VIB – CHEMICAL PROPERTIES
. In high temperature, Cr, Mo, W react with others halogen.
GROUP VIB – CHEMICAL PROPERTIES
• React with non-metallic elements in high temperature
W + N2 → WN2 ( 2000oC – 2500oC )
Mo + C → MoC ( > 800oC )
W + C → WC (> 1400oC )
• No effect with hydrogen
GROUP VIB – CHEMICAL PROPERTIES
• React with water at high temperatures
2Cr + 3H2O → Cr2O3 + 3H2 Mo + 2H2O → MoO2 + 2H2 W + 2H2O → WO2 + 2H2
• Chromium can dissolve in dilute solution of HCl and H2SO4
Cr + 2HCl → CrCl2 + H2 ( Eo Cr
2+/Cr = -0.91V )
• Mo and W are not effective with HCl and H2SO4
GROUP VIB – CHEMICAL PROPERTIES
W + 8HF +2HNO3 → H2WF8 + 2NO + 4H2O
Mo + Na2CO3 + 3NaNO3 → Na2MoO4 + 3NaNO2 + CO2
Ionic Radius
0.87 Å Cr2+ coordination number = 6; low spin0.94 Å Cr2+ coordination number = 6; high spin
0.755 Å Cr3+ coordination number = 60.55 Å Cr4+ coordination number = 40.69 Å Cr4+ coordination number = 60.40 Å Cr6+ coordination number = 40.58 Å Cr6+ coordination number = 6
GROUP VIB – CHEMICAL PROPERTIES
In coordination compound
GROUP VIB – CHEMICAL PROPERTIES
• The metal also forms many compounds of intense colour:
Chromates (e.g. Na2CrO4, PbCrO4) – Yellow
sodium chromate
Dichromates (e.g K2Cr2O7) ............. Orange-red
potassium Dichromate
GROUP VIB – CHEMICAL PROPERTIES
Chromic acid, CrO3 .......................... Red
Chromic acid
Chromium(III) oxide, Cr2O3 .............. Green
Chromium(III) oxide
GROUP VIB – BIOLOGYCAL ROLE
• Chromium is trace element
• Biologically active form of chromium (III) might play a role in the insulin signaling pathway
Chromium
GROUP VIB – BIOLOGYCAL ROLE
Molybdenum
• The reaction that nitrogenase enzymes perform is:
N2 + 8H+ +8e- + 16ATP + 16H2O → 2 NH3 + H2 + 16 ADP + 16Pi
• Molybdenum is cofactor enzymes
GROUP VIB – BIOLOGYCAL ROLE
• Human dietary intake and deficiency
People deficient molybdenum are prone to toxic reactions to sulfites in foods
Molybdenum is also present within human tooth enamel and may help prevent its decay.
Pork, lamb, and beef liver, include green beans, eggs, sunflower seeds, wheat flour, lentils, cucumbers and cereal grain.
GROUP VIB – BIOLOGYCAL ROLE
• Related diseases
Congenital molybdenum cofactor deficiency disease, seen in infants
Neurological damage.
GROUP VIB – BIOLOGYCAL ROLE
• Used by some bacteria, but not in eukaryotes
Tungsten
• Tungsten-using enzymes reduce carboxylic acids to aldehydes.
• Tungsten has been studied as a biological copper metabolic antagonist
GROUP VIB – APPLICATION IN LIFE
Chromium
• Metallurgy
GROUP VIB – APPLICATION IN LIFE
Dye and pigment
Wood preservative
Tanning
Refractory material
Catalysts
GROUP VIB – APPLICATION IN LIFE
Alloys
Molybdenum
Used as a fertilizer for some plants
Certain low voltage X-ray sources
GROUP VIB – APPLICATION IN LIFE
Tungsten
Hard materials
Alloys
Armaments
Niche uses
Gold substitution
Electronics
GROUP VIB – GROUP VIB – CHROMIUM COMPOUNDS
• Chromium(II) oxide (CrO) is a black powder
• Hypophosphites may reduce chromium(III) oxide to chromium(II) oxide
H3PO2 + 2 Cr2O3 → 4 CrO + H3PO4
• CrO is a basic oxide : CrO + 2HCl -> CrCl2 + H2O
• CrO is a reducing agent: CrO + 4HNO3 c Cr(NO3)3 + NO2 + 2H2O
Chromium(II)
GROUP VIB – CHROMIUM COMPOUNDS
Chromium(III) oxide
• One of principal oxides of chromium
Cr2O3
• Used as a pigment
• Occurs as the rare mineral eskolaite
eskolaite
GROUP VIB – CHROMIUM COMPOUNDS
• Chromium(III) oxide is amphoteric . It dissolves in concentrated alkali to yield chromite ions.
Cr2O3 + 6HCl -> 2CrCl3 + 3H2O
Cr2O3 + 2NaOHc + 3H2O -> 2Na[Cr(OH)4]
GROUP VIB – CHROMIUM COMPOUNDS
Preparation
• Potassium dichromate with sulfur at high temperatures
K2Cr2O7 + S Cr2O3 + K2SO4
• Decomposition of chromium salts
(NH4)2Cr2O7 N2 + Cr2O3 + 4H2O
GROUP VIB – CHROMIUM COMPOUNDS
Chromium(VI) oxide
• Has chromium in its +6 oxidation state
• It is a dark red crystalline solid used in cleaning glass
GROUP VIB – CHROMIUM COMPOUNDS
• Properties
It is a strong oxidizing agent
Can ignite alcohol
Very toxic and irritates skin.
Chromium(VI) oxide
Stronger oxidizing agent than chromate
It dissolves in water to make chromic acid and dichromic acid :
CrO3 + H2O -> H2CrO4
2CrO3 + H2O -> H2Cr2O7
Reacts with strong bases to make chromates :
CrO3 + 2NaOH -> Na2CrO4 + H2O
GROUP VIB – CHROMIUM COMPOUNDS Chromium(VI) oxide
GROUP VIB – CHROMIUM COMPOUNDS
• Preparation
Normally made by reacting sodium chromate or potassium chromate with sulfuric acid
Chromium(VI) oxide
GROUP VIB – CHROMIUM COMPOUNDS
Application
Application
• Used to clean glass
• Used to plate chromate on things.
• Reacts with metals to make a metal chromate
GROUP VIB – CHROMIUM COMPOUNDS
Safety
• A dangerous hazard to the environment.
• A carcinogen and can cause mutations
• Chromium(VI) oxide is very toxic and irritating
GROUP VIB – CHROMIUM COMPOUNDS
Chromate and Dichromate
• Chromate, CrO42-, is a salt of chromic acid
• Yellow color in basic conditions.
A sample of potassium chromate
GROUP VIB – CHROMIUM COMPOUNDS
Chromate and Dichromate
• Dichromate, Cr2O72-, is a salt of dichromic acid
• Strong orange color in acidic conditions.
A sample of potassium dichromate
GROUP VIB – CHROMIUM COMPOUNDS
• Strong oxidizing agent but it is a bad precipitating agent.
• Used as a precipitating agent but it is a poor oxidizing agent.
Chromate and Dichromate
2CrO42− (s) + 2H+(aq) H⇌ 2O(l) + Cr2O7
2− (aq) Kc=3.2×1014
• In acidic solution, the forward reaction is favored. In basic solution, the reverse reaction is favored.
GROUP VIB – CHROMIUM COMPOUNDS Chromate and Dichromate
2Na2CrO4 + H2SO4 -> Na2Cr2O7 + Na2SO4 + H2O
Na2Cr2O7 + 2NaOH -> 2Na2CrO4 + H2O
GROUP VIB – CHROMIUM COMPOUNDS Chromate and Dichromate
6FeSO4 + K2Cr2O7 + 7H2SO4 -> 3Fe2(SO4)3 + K2SO4 + Cr2(SO4)3 + 7H2O
• In acidic environment, salts of chromate and dichromate are strong oxidizing agents:
GROUP VIIB - INTRODUCTION1) Overview:
MANGANESE (Mn) TECHNETIUM (Tc) RHENIUM (Re)
GROUP VIIB – PHYSICAL PROPERTIES
• Manganese
- Hard metal - Lustrous silver-blue - Mp: 1519 / Bp: 2235
• Technetium
- Silver - Mp=2430, Bp = 5150
• Rhenium
- Silver, - Often encoutered as grey powder, - Mp = 3459, Bp = 5900.
GROUP VIIB – PHYSICAL PROPERTIESSources
Manganese:
• The 5th most abundant metal in Earth’s crust.
• Pyrolusite (MnO2) and rhodochrosite (MnCO3).
Pyrolusite (MnO2) rhodochrosite (MnCO3)
GROUP VIIB – CHEMICAL PROPERTIES
Technetium
• Uranium nuclear fuel reaction.
Rhenium
• In platinum ores.
uranium ores.
platinum ores
Sources
• Doesn’t accur in nature as uncombined
GROUP VIIB – CHEMICAL PROPERTIESManganese
1. With O2:
3Mn(s) + 2O2(g) → Mn3O4(s)
2. With halogen:
Mn(s) + Cl2(g) → MnCl2(s)
Mn(s) + Br2(g) → MnBr2(s)
Mn(s) + I2(g) → MnI2(s)
- Moderately active metal
3. With nitrogen
3Mn(s) + N2(g) → Mn3N2(s)
GROUP VIIB – CHEMICAL PROPERTIES
5. In water, Mn slowly attack with H2O
6. In the first row of d-block metal, Mn has the widest range of oxidation states, from II to VII.
4. React with Oxygen
4Tc + 7O2 → 2Tc2O74Tc + 7O2 → 2Tc2O7
GROUP VIIB – COMPOUNDS Manganese (II) [3d5]
• Manganese (II) oxide MnO (green solid):
Basic oxide Insoluble in water Soluble in acids, give pink solution, contain
[Mn(H2O)6]2+
Manganese (II) oxide
GROUP VIIB – COMPOUNDS
• Ion Mn2+ is easy to be oxidize.• Mn(OH)2 : white, rapidly dark in air as the reaction
4Mn(OH)2 + O2 2Mn2O3 + 4H2O
• Mostly salts of Mn is soluble in water. MnSO4 is very stable, MnPO4 and MnCO3 are sparingly soluble.
Manganese (II) [3d5]
→
• Manganese (III) oxide Mn2O3
MnO2 |1070K| Mn2O3
• Ion Mn3+ is less unstable in the presece of high concentration of Mn2+ or H+ ion
2Mn3+ + 2H2O Mn2+ +MnO2 + 4H+
GROUP VIIB – COMPOUNDS Manganese (III) [3d4]
→
→
• Manganese dioxide MnO2
Inert in most acids except when heating, but not dissolve to give Mn4+ (cause of the oxidizing characteristic)
MnO2 + 4HCl MnCl2 + Cl2 +2H2O
• With H2SO4 in 110°C:
2MnO2 + 2H2SO4 2MnSO4 + O2 + H2O
+ With KOH in high temperature
4KOH + O2 + 2MnO2 2K2MnO4 + 2H2O
GROUP VIIB – COMPOUNDS Manganese (IV): [3d3]
→
→
→
• The only oxohalide is MnOCl3
• In moist air, MnOCl3 hydrolyses to [MnO4]3-
• Salt of [MnO4]3- is blue and moisture-sensitive and easily react with H+ even H2O
2[MnO4]3- + 2H2O [MnO4]2- + MnO2 + 4[OH]-3[MnO4]3- + 8H+ [MnO4]- + 2MnO2 + 4H2O
GROUP VIIB – COMPOUNDS Manganese (V) [3d2]
→
→
• Ion MnO42- have deep green color and is unstable in acid medium, even in H2CO3:
3MnO42- + 4H+ 2MnO4- + MnO2 + 2H2O
• K2MnO4 is a powerful oxidizing agent, usually used in organic chemistry experiment.
GROUP VIIB – COMPOUNDS Manganese (VI): [3d1]
→
GROUP VIIB – COMPOUNDS
Most common is KMnO4: purple, strong oxidizing
4MnO4- + 4H+ 3O2 + MnO2 + 2H2O
Manganese (VII): [3d0]
→
• Oxide:
* Re2O7 is a yellow volatile oxide, hygroscopic compound.It dissolves in water as the reaction:
Re2O7 + H2O 2HReO4
• Halogenide:
ReCl5 + 3Cl2O ReO3Cl + 5Cl2
Tc2O7 + 4HF 2TcO3F + H3O+ + [HF2]-
GROUP VIIB – COMPOUNDS Compound of Technetium and Rhenium
→
→
→
GROUP VIIB –
The equilibrium constants for the formation od Mn(II) complexes are relatively low as Mn2+ ion has no ligand field stabilization energy. However, chelating ligand (ox, en, EDTA4-), form complexes isolable form aqueous solution. Some ex: [MnX4]2-, [MnCl6]4- (salt of Na and K).
Only very strong ligand fields give rise to spin pairing as in the ion [Mn(CN)6]4- and [Mn(CNR)6]2+
which have only one unpaired electron.
Mananese (II):
Coordination compound
GROUP VIIB –
Complexes are probably important in photosynthesis, where oxygen evolution depend on Mn.
Mn (III) and Mn (IV)
Coordination compound
GROUP VIIB – Coordination compound
In HCl solution, ReO4- is reduced by hypophosphite, partically to the chloro complexe ion [ReCl6]2- partically to [Re2Cl8]2- ion.
Technetium and Rhenium
GROUP VIIB – APPLICATION IN LIFE
• Essential element in all living things.Many type of enzyme contain Mn
• In human body:+ Our body contain about 12 mgs of Mn.+ We need to take 4 mgs Mn per day, from nuts, bran, wholegrain cereals, tea and parsley.+ Without Mn, bones grow spongier and break more easily.+ Essential for utilisation vitamin B1.
Manganese
GROUP VIIB – APPLICATION IN LIFE
Manganese
GROUP VIIB – APPLICATION IN LIFE
• The gamma – gray Tc is widely used for medical diagnostic studies.
• Corrosion inhibitor for steel.
• Using limited to close systems as Te radio.
Technetium
GROUP VIIB – APPLICATION IN LIFE
• Used for oven filaments and x-ray machines.
• Used as an electrical contact material.
• Used in nickel alloys to make single-crystal turbine blades.
Rhenium
GROUP VIIB – APPLICATION IN LIFE
• In steel production : Steel with 1% Manganese : stronger, improve
workability and resistance to wear. Steel with 13% Manganese : very strong and
used for railway, prison bar…• MnO2: used as catalyst, a rubber addition and
to decolourise glass that is green by ion impurities.
• MnSO4: make a fungicide.• MnO: powerful oxidizing agent used in
quantitative analysis.• Used in water purification and economical
bleaching.
Manganese
• MnO2: used as catalyst, a rubber addition and to decolourise glass that is green by ion impurities.
• MnSO4: make a fungicide.
• MnO: powerful oxidizing agent used in quantitative analysis.
• Used in water purification and economical bleaching.
GROUP VIIB – APPLICATION IN LIFE
Manganese
Iron (Fe) Cobalt (Co) Nickel (Ni)
GROUP VIII - INTRODUCTION1) Overview:
Ruthenium (Ru) Rhodium (Rh) Palladium (Pd)
Osmium (Os) Iridium (Ir) Platinum (Pt)
PlatinumGroupMetals(PGMs)
GROUP VIII - INTRODUCTION1) Overview:
Iron:
• Fourth most abundant element in the Earth’s crust
• 3 allotropes of iron is: α-iron (alpha-iron); γ-iron (gamma-iron); and δ-iron (delta-iron).
• Iron is used since prehistoric ages.
GROUP VIII - INTRODUCTION1) Overview:
Cobalt:
• The name in German is ‘kobalt’, which is goblin.
• It is the 30th most abundant in crustal rocks.
GROUP VIII - INTRODUCTION1) Overview:
Nickel:
• Is frequently used in coinage in nickel-copper alloys.
• It is the 22nd most abundant in crustal rocks.
• Raney Nickel, an alloy of Aluminum and Nickel, is an important catalyst in organic chemistry.
GROUP VIII - INTRODUCTION1) Overview:
Platinum Group Metals (PGMs)
• PGMs are often used in jewelry• Catalytic prperties of PGMs are well-known
GROUP VIII - INTRODUCTION1) Overview:
Platinum Group Metals (PGMs)
• Catalytic properties are important in organic chemistry
GROUP VIII - INTRODUCTION2) Natural resouces:
Iron:
Hematite (Fe2O3) Magnetite (Fe3O4)
Limonite (Fe,Ni)O(OH) Siderite (FeCO3)
GROUP VIII - INTRODUCTION2) Natural resouces:
Cobalt:
Cobaltite (CoAsS) Skutterudite ((Co,Ni,Fe)As3)
Erythrite (Co3(AsO4) 8H2O)
GROUP VIII - INTRODUCTION2) Natural resouces:
Nickel:
Garnierite (Ni, Mg)3Si2O5(OH)4)
Limonite (Fe,Ni)O(OH)
Pentlandite ((Ni, Fe)9S8)
GROUP VIII – PHYSICAL PROPERTIES
Iron
White, lustrous metal
Magnetic
Conductorial
Refractory
GROUP VIII – CHEMICAL PROPERTIES
Iron:• Reaction with air to form
various oxide and hydroxide compounds.
• Fe is pyrophoric in air, but the bulk metal is oxidized only when heated.
• Iron reacts on mild heating with a variety of other non – metals (halogens, S, P, B, C, Si)
2Fe + 3X2 → 2FeX3 (X = F, Cl, Br)Fe + 2S → FeS2 (Fool’s gold)
GROUP VIII – CHEMICAL PROPERTIES
Iron:• Ferrous halides react with binary halogen acid:
Fe + 2 HX → FeX2 + H2
• Reaction with acids:2Fe + 6H2SO4conc → Fe2(SO4)3 + 3SO2 + 6H2O
• Fe also takes part in replacing reactions.Fe + 2AgNO3 deficiency → Fe(NO3)2 + 2Ag
• At high temperature, Fe reduces steam: 3Fe + 4H2O → Fe3O4 + 4H2 (<570oC)
Fe + H2O → FeO + H2 (>570oC)
GROUP VIII – CHEMICAL PROPERTIES
Iron VI, V and VI:• The highest oxidation states of iron are found in
compounds of [FeO4 ]2- , [FeO4]3- , [FeO4]4- and [FeO3]2-
• Ferrate(VI) is a powerful oxidant.[FeO4]2- + 8H+ + 3e- → Fe3+ + 4H2O
• The reaction of K2FeO4 with KOH in O2 at 1000 K gives K3FeO4, a rare example of an Fe(V) salt.
• Iron(IV) ferrates include Na4FeO4 (made from Na2O2 and FeSO4), Sr2FeO4 (prepared by heating Fe2O3 and SrO in the presence of O2) and Ba2FeO4 (made from BaO2 and FeSO4).
GROUP VIII – CHEMICAL PROPERTIES
Iron III• Name is ferric
• Iron (III) halides are made by heating iron with halogens.
• Iron (III) oxide is insoluble in water, but dissolves in acid.
• Iron (III) salts and oxide creates Fe2O3.H2O (also written as Fe(O)OH) but often mistaken as Fe(OH)3.
FeCl3 + 3NaOH → Fe(OH)3 + 3NaCl
Iron II• Common name is ferrous.
• Iron (II) halides are made by dissolving the metal in binary halogenic acid. Fe + 2HX → FeX2 + H2
GROUP VIII – CHEMICAL PROPERTIES
Cobalt:• Reaction with air:
3Co(s) + 4O2(g) → 2Co3O4(s)2Co(s) + O2(g) → 2CoO(s)
• With oxygen with steam as a catalyst:2Co(s) + O2(g) → 2CoO(s)
• With halogens: Co(s) + Br2(l) → CoBr2(s) [green]
• With acids:Co(s) + H2SO4(aq) → Co2+(aq) + SO4
2-(aq) + H2(g)
GROUP VIII – CHEMICAL PROPERTIES
Cobalt compounds:• With aqua and halogen ligands:
[Co(H2O)6]2+ + 2NH3→[Co(H2O)4(OH)2] (pink) +2NH4+
[Co(H2O)6]2+ + 6NH3→[Co(NH3)6]2+ (brown) + 6H2O
[Co(H2O)6]2+ (pink) + 4Cl− ⇌ [CoCl4]2− (blue) + 6H2O
• With halides: - Anhydrous cobalt dichloride is blue, but the hydrate form is red.
GROUP VIII – CHEMICAL PROPERTIES
Nickel:• With acids:
Ni + HCl → NiCl2 + H2
Nickel is passive in concentrated HNO3
• Nickel doesn’t react with aqueous alkalis.
• With air: they react with each other in high temperature.Ni + H2O → H2 + NiO
• With halogens: Nickel forms Ni(II) halides with halogens,But with F2, the halide layer prevent further attack.
Nickel compounds:• Organometallic species: usually in low oxidation states.
Nickel is passive in concentrated HNO3
• Ni(II) compounds are important species:
[Ni(NH3)6]2+ [Ni(en)]2+ [NiCl4]2− [Ni(H2O)6]2+
Green Ni(OH)2 is used in NiCd batteries
• Ni(IV) compounds are formed under influence of really strong oxidants. Ex: KNiO6 is formed under oxidation of [Ni(H2O)6]2+ by [S2O8]2- with [IO4]-
• Ni(I) is uncommon: ex [Ni2(CN)6]4-
GROUP VIII – CHEMICAL PROPERTIES
Iron:• Making steel.• Hemoglobin in blood and myoglobin in
muscle• Essential for energy production
(respiratory chain)• DNA Replication• Glucose Metabolism• Enzyme systems
GROUP VIII – APPLICATIONS
Cobalt:• Making magnets and batteries• Other alloys of cobalt are used in jet
turbines and gas turbine generators• Used in electroplating• Cobalt salts produce brilliant blue colours
for many uses.
Roles (in Biology)• Trace element Part of the active site of
vitamin B12 • Cancer treatment and preserve food
(Radioactive 60Co)• Correct mineral deficiencies (animals)
GROUP VIII – APPLICATIONS
Nickel:
• It is used in coinage, plating, alloys.• A trace mineral in human and animal body.• Low nickel: reduced growth, decreased life
expectancy, reduced iron absorption leads to anaemia.
• Low nickel in human body can interrupt absorption of calcium into the skeleton.
• Key component in hydrogenase biosynthetic processes.
• Nickel is found in urease – an enzyme that assist plant hydrolyse urea.
GROUP VIII – APPLICATIONS
GROUP VIIIB – NATURAL RESOURCESIRON:
Iron is the second cheapest most abundant metal Nearly 5.6% of Earth’s crust. Major iron ores are hematite, Fe2O3, magnetite,
Fe3O4, limonite, FeO(OH), and siderite, FeCO3. Pure iron is almost never found in nature.
GROUP VIIIB – NATURAL RESOURCESRUTHENIUM:
Ru is found in nature with the other platinum group. Commercially, it is obtained from pentlandite (a sulfide of iron and nickel) with contains small quantities of ruthenium.
OSMIUM: Osmium occurs uncombined in nature and also in
the mineral osmiridium (an alloy with iridium). Most osmium is obtained commercially from the wastes of nickel refining.
GROUP VIIIB – CHEMICAL PROPERTIESRUTHENIUM & OSMIUM
React with O2:Ru + O2 (>870) RuO2 (non-volatile)Os+ O2 (>870) OsO4 (volatile) Reacte with F2 and Cl2 when heated.
Attacked by mixtures of HCl and oxidizing agents, and by molten alkalis.
Metals:
GROUP VIIIB – CHEMICAL PROPERTIESRUTHENIUM & OSMIUM
Ruthenium(VIII) oxide RuO4 and Osmium(VIII) oxide OsO4 is unstable and also a very powerful oxidant.
All the binary halides RuX3 are known but for Os, only OsCl3 and OsI3 have been established; OsF4 is the lowest fluoride of Os.
Binary halides of Ru(II) and Os(II) are not well characterized and there are no oxides
Compounds:
GROUP VIIIB – CHEMICAL PROPERTIESRUTHENIUM & OSMIUM
Most of the chemistry of Ru(II) and Os(II) concerns complexes: diamagnetic, low-spin d6, octahedral.
Many low oxidation state complexes of Ru and Os including those of Ru(II) and Os(II) are stabilized by PR3 ( -acceptor) ligands.π
Complexes:
GROUP VIIIB – BIOLOGICAL ROLEIRON:
In biological systems, these oxidation states are limited primarily to the ferrous (+2), ferric (+3) and ferryl (+4) states. Iron required for Hemoglobin in blood Needed for Myoglobin in muscle Essential for energy production (respiratory chain) DNA Replication Glucose Metabolism Enzyme systems in the body that use iron include
Mono - and Di – Oxygenases, protective Peroxidases like catalase and Myeloperoxidase and Several Oxidoreductases.
Foods contain Fe:
GROUP VIIIB – BIOLOGICAL ROLERUTHENIUM:
Ruthenium has no known biological role. Ruthenium(IV) oxide is highly toxic.
OSMIUM: Osmium has no known biological role. The metal is
not toxic, but its oxide is volatile and very toxic, causing lung, skin and eye damage.
GROUP VIIIB – APPLICATIONIRON:
In industry: - Be used to make steel.- Be the manufacture of tools and weapons.In medicine: Iron is usually administered orally to a patient as iron supplement tablets containing an Fe(II) or Fe(III) salt. Iron(II) salts are more typical because they exhibit better solubilities than Fe(III) salts at physiological pH, but Fe(III) has the advantage that, unlike Fe(II), it is not susceptible to oxidation in aqueous solution.
GROUP VIIIB – APPLICATIONRUTHENIUM: Used in electronics industry for chip resistors and
electrical contacts. Used for catalysts for ammonia and acetic acid
production. Used in solar cells, which turn light energy into
electrical energy. Used in some jewellery as an alloy with platinum.
OSMIUM:
Used to produce very hard alloys for fountain pen tips, instrument pivots, needles and electrical contacts
Used in the chemical industry as a catalyst.
GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Metals:
Resistant to corrosion. Pt is more inactive than Pd. Pd reacts with O2, F2 and Cl2 at high temperature. Both can be attacked by aqua regia and molten alkali
metal oxide. Pt + 2 HNO3+ 6 HCl + Cl2 → + 3 H2O + 1/2 O2 +
H2PtCl6 (chloroplatinic acid) + 2 NOCl M(II) and M(IV) are two common oxidation state.
GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Compounds – M(IV) compounds:
All the M(IV) halides are known M + 2X2 MX4 M(IV) is stable for Pt than Pd. Chloroplatinic acid is a great starting material
GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Compounds – M(II) compounds:
Halides of Pd(II) and Pt(II) except PtF2 are known. M(Cl)2 is the precursor for preparation of other
compounds. MCl2 + F2 -> MF¬4 Cisplatin is an anticancer chemical
GROUP VIIIB – CHEMICAL PROPERTIESPALADIUM & PLATINUM Compounds:
+4 and +5 are the highest oxidation numbers for the two metals.
MBr3 and other M(III) species are mixed-valence compounds.
GROUP VIIIB – BIOLOGICAL ROLENICKEL:
A trace mineral.(Low nickel: reduced growth, decreased life expectancy, reduced iron absorption leads to anaemia. Low nickel in human body can interrupt absorption of calcium into the skeleton.) Key component in hydrogenase biosynthetic
processes. Nickel is found in urease – an enzyme that assist
plant hydrolyse urea.
GROUP VIIIB – BIOLOGICAL ROLE
PALADIUM: Toxic???
PLATINUM: Beside Cisplatin and Carboplatin, Oxaliplatin is also
used in chemotherapy. Platinum salts can be carcinogens, or cause allergy,
deafness, stimulation to dangerous chemicals in human body, such as selenium.
GROUP VIIIB – APPLICATIONNICKEL:
Used to plate other metals to protect them. Used in making alloys such as stainless steel Used in toasters and electric ovens. Nickel is used in batteries. Used as a catalyst for hydrogenating vegetable oils.
Adding nickel to glass gives it a green colour.
GROUP VIIIB – APPLICATIONPALADIUM:
PLATINUM: