Transition metals
Common properties
The transition metals have these properties in common:
* They are metals.
* They form coloured compounds.
* They are good conductors of heat and electricity.
* They can be hammered or bent into shape easily.
* They are less reactive than alkali metals such as sodium, they have higher melting points (but mercury is a liquid at room temperature) and they are hard and tough.
* They have high densities.
Iron
The chemical symbol for iron, Fe, comes from the Latin word for iron - ferrum. Iron is the second most abundant metal in the Earth's crust (aluminium is the most abundant metal). The core of the Earth is solid iron, and iron is found in meteorites, but in the Earth's crust iron is found mainly as minerals of iron oxide - hematite, magnetite, goethite and limonite. The mineral which is mostly used as ore for making iron is hematite. Its chemical formula is Fe2O3.
Iron is about 8 times heavier than water (its relative density is 7.87). When iron is exposed to the air it starts to turn back into iron oxide and the red powder that forms on the surface of iron is what we call rust. You may have seen rust on old cars or old iron sheds or roofs. To make iron stronger and less likely to rust it can be combined with carbon and other elements to make steel.
The mineral magnetite is very magnetic, and if you dangle a piece on a length of string it will orient itself north-south. Iron and some alloys of iron are also magnetic.
The Properties of Iron
Chemical Symbol:
Fe
Mineral:
iron oxides: eg hematite and magnetite
Relative density:
7.87
Malleability:
High
Ductility:
High
Melting point:
535°C
Atomic Mass:
55.85
Uses
Iron is the most used of all the metals, comprising 95 percent of all the metal tonnage produced worldwide. Its combination of low cost and high strength make it indispensable, especially in applications like:
* Hospital equipment
* Cans & containers
* Engine cylinder blocks
* Motor vehicle parts
* Roofing
* Motor vehicle
* Machinery
* Bodies
* Buildings
* Cutlery
* Drill bits
* Boats
* Metal ...
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535°C
Atomic Mass:
55.85
Uses
Iron is the most used of all the metals, comprising 95 percent of all the metal tonnage produced worldwide. Its combination of low cost and high strength make it indispensable, especially in applications like:
* Hospital equipment
* Cans & containers
* Engine cylinder blocks
* Motor vehicle parts
* Roofing
* Motor vehicle
* Machinery
* Bodies
* Buildings
* Cutlery
* Drill bits
* Boats
* Metal cutting tools
* Transportation
* Woks
* Camp ovens
* Household appliances
Titanium
Titanium is lightweight, strong and rust-resistant. Titanium is a silver-white metal.
Pure titanium is quite soft but titanium alloys are extremely strong (even stronger than steel and aluminium). Titanium has a very high melting point.
Titanium is non-toxic. Titanium was named in 1795 by a German chemist, after the Titans of Greek mythology who were very strong. Its symbol is Ti.
Titanium dioxide is one of the whitest, brightest substances known. It is non-toxic. It also provides protection from UV rays.
Uses
The following uses for titanium are gathered from a number of sources as well as from anecdotal comments. I'd be delighted to receive corrections as well as additional referenced uses (please use the feedback mechanism to add uses).
Titanium is used for alloys with with aluminium, molybdenum, manganese, iron, and other metals. These alloys of titanium are used principally in the aerospace industry, for both airframes and engines, where lightweight strength and ability to withstand extremes of temperature are important. Titanium is as strong as steel, but much lighter. It is twice as strong as aluminium. It is nearly as resistant to corrosion as platinum. Titanium is a component of joint replacement parts, including hip ball and sockets.
It has excellent resistance to sea water and is used for propeller shafts, rigging, and other parts of ships exposed to salt water. A titanium anode coated with platinum provides cathodic protection from corrosion by salt water. Titanium paint is an excellent reflector of infrared radiation, and is extensively used in solar observatories where heat causes poor viewing conditions.
Pure titanium dioxide is relatively clear and has an extremely high index of refraction with an optical dispersion higher than diamond. It is produced artificially for use as a gemstone, but it is relatively soft. Star sapphires and rubies exhibit their asterism as a result of the presence of TiO2. The dioxide is used extensively for paint as it is permanent and has good covering power. Titanium oxide pigment accounts for the largest use of the element.
Copper
The word copper comes from the Latin word "cuprum", which means "ore of Cyprus". This is why the chemical symbol for copper is Cu.
Copper is the only naturally occurring metal other than gold that has a distinctive colour. Like gold, copper is an excellent conductor of heat and electricity. It is also very malleable and ductile.
Copper is easily mixed with other metals to form alloys such as bronze and brass. Bronze is an alloy of tin and copper, and brass is an alloy of zinc and copper.
Copper is also resistant to corrosion (it does not rust very easily).
The Properties of Copper
Chemical Symbol:
Cu
Mineral:
most commonly found as chalcopyrite
Relative density:
8.96
Hardness:
2.5-3 on Mohs scale
Malleability:
High
Ductility:
High
Melting point:
083°C
Atomic Mass:
64
Uses
Copper is malleable and ductile, and is used extensively, in products such as:
* Copper wire.
* Copper plumbing.
* Doorknobs and other fixtures in houses.
* Electromagnets.
* Motors, especially electromagnetic motors.
* Watt's steam engine.
* Vacuum tubes, cathode ray tubes, and the magnetrons in microwave ovens.
* Wave guides for microwave radiation.
* There is increasing use of copper in integrated circuits, replacing aluminum because of its superior conductivity.
* As a component of coins, often as cupronickel alloy.
* In cookware, such as frying pans.
* Most flatware (knives, forks, spoons) contains some copper (nickel silver).
* Sterling silver, if it is to be used in dinnerware, must contain a few percent copper.
* As a component in ceramic glazes, and to color glass.
* Musical instruments, especially brass instruments.
* Copper (II) sulfate is used as a poison and a water purifier. It is used in gardening powders and sprays to kill mildew.
Catalysts
A catalyst is defined as a substance which alters the rate of a reaction, but doesn't go any permanent chemical change itself. For example, hydrogen iodide decomposes to hydrogen and iodine. In the presence of platinum metal, this decomposition is much faster. Our bodies contain thousands of catalysts which are often called enzymes. These organic catalysts allow reactions to occur which are essential to life, but which would occur too slowly if they were not catalysed. Catalysts provide a different pathway for the reaction which has a lower activation energy than before. If a reaction has a low activation energy, its rate tends to be higher. As an example of a different pathway, when propanone (H3C - CO - CH3) is reacting with iodine in water, it reacts faster in acid conditions. Protons in solution are a catalyst of the reaction. With acid conditions, the propanone is more likely to be protonated which allows a different and lower activation energy pathway to the iodination of the propanone.
Many transition metals are used directly as catalysts in industrial chemical processes and in the anti-pollution catalytic converters in car exhausts.
For example iron is used in the Haber Synthesis of ammonia:
Nitrogen + Hydrogen ==> Ammonia (via a catalyst of Fe atoms)
or N2(g) + 3H2(g) ==> 2NH3(g)
Platinum and rhodium (in other transition series below Sc-Zn) are used in the catalytic converters in car exhausts to reduce the emission of carbon monoxide and nitrogen monoxide, which are converted to the non-polluting gases nitrogen and carbon dioxide.
2NO(g) + 2CO(g) ==> N2(g) + 2CO2(g)
Nickel is the catalyst for 'hydrogenation' in the margarine industry. It catalyses the addition of hydrogen to an alkani carbon=carbon double bond (>C=C< + H2 => >CH-CH<). This process converts unsaturated vegetable oils into higher melting saturated fats which are more 'spreadable' with a knife!
As well as the metals, the compounds of transition metals also acts as catalysts.
For example manganese dioxide (or manganese(IV) oxide), MnO2, a black powder, readily decomposes an aqueous solution of hydrogen peroxide:
Hydrogen peroxide ==> water + oxygen
or 2H2O2(aq) ==> 2H2O(l) + O2(g)
