Metals, extraction, compounds and alloys
General properties and useful exceptions
Many metals conduct heat and electricity, are malleable and form positive ions in familiar compounds. These behaviours relate to metallic bonding and mobile delocalised electrons, but metals differ greatly in , strength, melting point and reactivity. An alloy is a material containing a metal combined with other element components to modify properties. Adding carbon to iron can change hardness and mechanical behaviour; adding chromium supports corrosion in stainless steels. Do not assume every metal reacts with water or every alloy has a fixed universal composition. Specific grades and uses depend on the required balance of properties.
Reactivity and extraction choices
Very reactive metals form compounds difficult to reduce chemically using carbon, so molten electrolysis is commonly needed for extraction. Less reactive metals can sometimes be obtained by carbon or carbon-monoxide , while some very unreactive metals occur partly native. An ore is a naturally occurring material from which a useful constituent can be extracted economically under relevant conditions. Concentration, chemical conversion, and refining are distinct stages. Sulfide ores may require roasting or other processing before final metal production. State the ore and reducing process asked for rather than applying 'heat with carbon' to every metal oxide.
Aluminium and its oxide
Bauxite is processed to produce alumina before electrolytic extraction. Alumina dissolves in molten cryolite-based to reduce the required operating temperature and improve process conditions compared with melting pure alumina alone. Aluminium ions gain electrons at the cathode, while carbon anodes are consumed through reactions involving oxygen-containing species. Aluminium is light and develops a protective oxide surface contributing to corrosion under many conditions. Aluminium oxide and hydroxide are amphoteric: they react with both suitable acids and strong bases. Distinguish that protective layer from a claim that aluminium never reacts. Powdered aluminium and some aluminium reactions require special precautions.
Iron extraction and steel
A blast furnace converts appropriate iron ore through reactions involving coke, hot air and limestone flux. Carbon monoxide is an important reducing agent for iron oxides. Limestone decomposes to calcium oxide, which reacts with suitable acidic impurities such as silica to form slag. Molten iron and slag separate by their properties within the furnace. Initial iron has a relatively high carbon content and can be refined to make steels with controlled carbon and alloying elements. Cast iron, wrought iron and steels differ in composition and uses; they are not merely names for perfectly pure iron. A balanced equation conserves both oxygen and carbon.
Copper, tin and refining
Copper can be extracted from suitable oxide ores by or from sulfide ores through more complex controlled processes. Electrolytic refining uses impure copper as an anode and deposits purer copper at a cathode under suitable conditions. Its high conductivity supports wiring uses, while corrosion behaviour and workable structure support other applications. Tin commonly occurs in cassiterite, SnO₂, and can be obtained by appropriate carbon after ore processing. Tin coatings and alloys have uses depending on composition and protective properties. A coating is not automatically sacrificial; protection after scratching depends on the metals' electrochemical relationship, not simply which one looks shinier.
Sodium compounds and the Solvay sequence
Sodium chloride is obtained from seawater, brines or mineral deposits through suitable separation and purification. Brine electrolysis can produce sodium hydroxide under industrial cell conditions. Sodium carbonate manufacture through the Solvay process exploits reactions and solubility differences involving brine, ammonia and carbon dioxide, with ammonia recovery. Heating sodium hydrogencarbonate produces sodium carbonate, carbon dioxide and water. Sodium carbonate is useful in glass manufacture and other processes. Sodium hydroxide is a strong alkali and can precipitate metal hydroxides; excess reagent dissolves some amphoteric hydroxides rather than every precipitate.
Calcium compounds, lime and cement
Heating suitable calcium carbonate materials, including limestone or shells under appropriate processing, gives calcium oxide and carbon dioxide. Calcium oxide reacts with water to form calcium hydroxide, releasing substantial . Lime-based mortar hardens partly through reaction with carbon dioxide, while Portland-type cement setting involves hydration of manufactured silicate and aluminate phases and is not simply drying. Calcium hydroxide solution is limewater and provides a carbon-dioxide test. Calcium carbonate has uses as a raw material and filler, depending on purity and particle properties. Distinguish quicklime CaO, slaked lime Ca(OH)₂ and limestone CaCO₃ rather than using lime for all three without clarification.
Transition metals, complexes and catalysis
Many first-series transition elements show variable states, coloured ions, complex formation and catalytic behaviour. These features relate to electronic structure and available states, though the simple definition and individual exceptions require care. A complex contains a central metal species bonded to surrounding ligands through donor interactions. Complex charge depends on metal state and ligand charges. Neutral ammonia ligands do not directly add ionic charge. In naming a complex, count ligands and identify the metal state according to the naming scheme used. Not every transition-metal compound is coloured, and colour alone cannot establish complete identity in a mixture.
Qualitative tests and familiar alloys
A sodium flame can give strong yellow colour, while calcium gives a characteristic brick-red or orange-red appearance under usual test conditions. With suitable hydroxide tests, Cu²⁺ gives a blue precipitate, Fe²⁺ a green precipitate that can oxidise on standing and Fe³⁺ a reddish-brown precipitate. Aluminium hydroxide is white and dissolves in excess strong hydroxide. Interpretation depends on reagent, concentration and interferences. Brass is mainly copper–zinc, bronze commonly copper–tin and soft solder can use tin-based compositions. Duralumin is aluminium-based, alnico contains aluminium, nickel and cobalt among its components, and permalloy is nickel–iron based. Connect properties to intended use.
Self-check with chemical reasoning
For Fe₂O₃, carbon monoxide is oxidised while iron(III) is reduced. For, the equation conserves atoms and illustrates carbon under the specified model; real furnace gases depend on conditions. A blue hydroxide precipitate supports Cu²⁺ within a controlled qualitative scheme, while a white amphoteric hydroxide needs further evidence to distinguish possible ions. Aluminium extraction needs electrolysis rather than carbon in the ordinary syllabus account because of alumina's high stability. Name the relevant reaction, particle or property rather than relying on a metal's position as a memorised label.