Metals And Non Metals-VI

A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution. In the reactivity series, copper (Cu) is less reactive than iron, zinc, and magnesium, but it is more reactive than silver (Ag). Therefore, copper can displace silver from a silver salt solution (e.g., AgNO₃). The reaction is: Cu(s) + 2AgNO₃(aq) → Cu(NO₃)₂(aq) + 2Ag(s). Copper cannot displace iron, zinc, or magnesium because they are more reactive than copper.
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When copper is exposed to moist air for a long time, it undergoes corrosion to form a green patina (coating). The green coating is primarily basic copper carbonate [CuCO₃·Cu(OH)₂], formed by the reaction of copper with atmospheric carbon dioxide, oxygen, and water: 2Cu + H₂O + CO₂ + O₂ → CuCO₃·Cu(OH)₂. This is seen on old copper roofs, statues (like the Statue of Liberty), and old copper utensils. Copper oxide (black) forms on heating in air, not by slow atmospheric corrosion. Copper sulphide is black, and copper chloride is greenish-blue but not the main patina in normal air.
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Rusting of iron requires both oxygen (from air) and water (or moisture) to be present simultaneously. The overall reaction is: 4Fe + 3O₂ + 2xH₂O → 2Fe₂O₃·xH₂O (hydrated iron(III) oxide). In dry air, oxygen is present but water is absent. Without water, the electrochemical corrosion process cannot occur because water acts as an electrolyte, facilitating the flow of electrons between anodic and cathodic sites on the iron surface. Carbon dioxide and nitrogen are not required for rusting.
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The purity of gold is measured in carats (karats). Pure gold is 24 carats (24K), meaning 24 out of 24 parts are gold (100% gold). 22-carat gold means that 22 parts out of 24 parts are gold, and the remaining 2 parts are other metals (usually copper, silver, or zinc). Therefore, 22K gold is 91.67% gold (22/24 × 100). Gold is alloyed with other metals because pure gold (24K) is too soft for making durable jewellery. 22K gold is commonly used in Indian jewellery.
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Magnesium oxide (MgO) is a basic oxide. Basic oxides are formed by metals and react with water to form bases (alkalis) or react with acids to form salt and water. When MgO dissolves in water, it forms magnesium hydroxide: MgO + H₂O → Mg(OH)₂, which turns red litmus blue. In contrast, CO₂ (carbon dioxide), SO₂ (sulfur dioxide), and NO₂ (nitrogen dioxide) are non-metal oxides and are acidic in nature; they dissolve in water to form acids (carbonic, sulfurous, and nitric acid respectively).
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When non-metals react with hydrogen, they form covalent compounds called hydrides. For example, nitrogen reacts with hydrogen to form ammonia (NH₃); sulfur forms hydrogen sulfide (H₂S); chlorine forms hydrogen chloride (HCl); carbon forms methane (CH₄). These are all hydrides of non-metals. Hydroxides are formed by metals (e.g., NaOH). Oxides are formed with oxygen. Salts are formed by neutralization reactions between acids and bases.
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Platinum, gold, and silver are noble metals located at the bottom of the reactivity series. They have excellent metallic lustre (shiny appearance) and are highly resistant to corrosion (tarnishing). They do not react with air, moisture, or most chemicals. Gold does not corrode at all; silver tarnishes slowly due to H₂S (forming black Ag₂S), but this is easily cleaned. Their lustre, rarity, malleability (can be shaped), and non-corrosive nature make them ideal for jewellery. They are not highly reactive, do not corrode easily, and are expensive, not cheap.
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Stainless steel is an alloy of iron (Fe) with a minimum of about 10.5% chromium (Cr) and often contains nickel (Ni) as well. Chromium forms a thin, adherent, invisible chromium oxide (Cr₂O₃) layer on the surface, which prevents rusting (passivation). Nickel improves corrosion resistance, strength, and provides a shiny appearance. Common types include 304 (18% Cr, 8% Ni) and 316 (16% Cr, 10% Ni, 2% Mo). Copper and zinc form brass; zinc and tin are used in some coatings; lead and tin form solder.
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When metals react with oxygen, they form metal oxides, which are generally basic in nature. Examples: Sodium forms Na₂O (sodium oxide), which dissolves in water to form NaOH (a base); magnesium forms MgO (magnesium oxide), which forms Mg(OH)₂ (a base); calcium forms CaO (calcium oxide), which forms Ca(OH)₂ (a base). These oxides neutralize acids to form salt and water. Non-metals form acidic oxides. Some metals (like Al, Zn) form amphoteric oxides (both basic and acidic). Gaseous oxides are usually from non-metals.
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A more reactive metal can displace a less reactive metal from its compound. In the reactivity series, zinc (Zn) is above copper (Cu), meaning zinc is more reactive. Therefore, zinc can displace copper from copper oxide (CuO). The reaction is a reduction-oxidation reaction: ZnO + C → Zn + CO is the extraction process, but for displacement: Zn + CuO → ZnO + Cu (when heated). Copper is less reactive, so it cannot displace itself. Gold and silver are below copper and cannot displace it.
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Copper is used for hot water tanks and plumbing because it is less reactive than iron and does not corrode easily. Copper does not react with water (even hot water) because it is below hydrogen in the reactivity series. It forms a protective oxide layer. Iron, in contrast, rusts readily in the presence of water and oxygen, especially at higher temperatures. Copper’s corrosion resistance, good thermal conductivity, and durability make it suitable for hot water tanks, despite being more expensive than iron.
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The corrosion of iron is specifically called rusting. Rust is the reddish-brown, flaky, hydrated iron(III) oxide (Fe₂O₃·xH₂O) that forms on the surface of iron when it reacts with oxygen and moisture. Galvanising is a method of preventing rust by coating iron with zinc. Alloying is mixing metals to improve properties. Tarnishing refers to the dulling of the surface of metals like silver (forming silver sulphide) or copper (forming green patina), not specifically iron corrosion.
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An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. The added substance can be a metal (e.g., copper added to gold to make 22K gold; tin added to copper to make bronze) or a non-metal (e.g., carbon added to iron to make steel). The non-metal is typically added in small proportions. Therefore, the alloying element can be either a metal or a non-metal, not just one category. Examples: Brass = Cu (metal) + Zn (metal); Steel = Fe (metal) + C (non-metal).
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Galvanisation is the process of coating iron or steel with a thin layer of zinc (Zn) to prevent rusting. Zinc is chosen because it is more reactive than iron. It acts as a sacrificial anode – even if the coating is scratched, the zinc corrodes preferentially, protecting the iron underneath. Zinc also forms a durable, adherent zinc oxide layer that provides a physical barrier. Tin is used for “tinning” (e.g., tin cans), but tin is less reactive than iron, so if scratched, iron rusts faster.
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Pure gold is 24 carat (24K) gold. It means 24 out of 24 parts are gold, i.e., 100% gold with no other metals added. However, 24K gold is very soft and malleable, making it unsuitable for making durable jewellery that will be worn daily. For jewellery, gold is alloyed with other metals (copper, silver, zinc) to increase hardness and durability. Common jewellery carats are 22K (91.67% gold) and 18K (75% gold). 24K gold is used for investment (coins, bars) and some traditional ornaments but is rare for daily-wear jewellery.
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Metallurgy is the broad scientific and technological process of extracting metals from their ores, purifying them (refining), and modifying their properties (e.g., through alloying). It encompasses all steps: mining, concentration of ore, extraction (reduction), refining, and sometimes alloying. Galvanisation is a specific corrosion prevention method. Alloying is mixing metals to form alloys. Corrosion is the deterioration of metals due to environmental reactions. Thus, metallurgy is the correct comprehensive term.
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Metals generally possess the properties of malleability (ability to be beaten into thin sheets) and ductility (ability to be drawn into thin wires). For example, gold is highly malleable and ductile; copper can be drawn into wires. Metals are not generally gaseous at room temperature (except mercury is liquid, but most are solid). They are lustrous (shiny), not dull. They are not brittle; brittleness is a characteristic of non-metals and some ionic compounds. Metals are typically hard (with some exceptions like sodium).
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Mercury (Hg) is the only metal that is liquid at standard room temperature (25°C). Its unique electron configuration (5d¹⁰6s²) results in relativistic effects that weaken the metallic bonding, preventing its atoms from being held together in a solid lattice at room temperature. Aluminium, sodium, and zinc are all solid metals at room temperature. Gallium and caesium have very low melting points (around 30°C) but are solid at typical room temperature (25°C). Mercury is used in thermometers, barometers, and switches.
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Zinc, magnesium, and copper are metals. When metals react with oxygen, they form metal oxides, which are generally basic in nature. Magnesium oxide (MgO) and copper(II) oxide (CuO) are basic oxides; they react with acids to form salt and water. Zinc oxide (ZnO) is actually amphoteric (reacts with both acids and bases), but it is typically classified under basic oxides in general metal oxide discussions. However, among the options, “basic oxides” is the correct classification for metal oxides in general. They are not gaseous, neutral, or primarily acidic.
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The term “amphoteric” comes from the Greek word amphoteroi, meaning “both.” An amphoteric oxide is one that can react with both acids and bases to form salt and water. Aluminium oxide (Al₂O₃) demonstrates this dual behavior: it reacts with hydrochloric acid (an acid) to form aluminium chloride and water (basic nature), and it also reacts with sodium hydroxide (a base) to form sodium aluminate and water (acidic nature). This property makes Al₂O₃ amphoteric. It is not simply basic or acidic, and it is insoluble in water.
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In the extraction of metals, carbonate and sulphide ores are first converted into metal oxides through calcination (for carbonates) and roasting (for sulphides). The reason is that metal oxides are much easier to reduce to the free metal than carbonates or sulphides. Reduction of oxides can be done using common reducing agents like carbon (coke) or carbon monoxide. For example, ZnO + C → Zn + CO is straightforward. Reducing ZnCO₃ or ZnS directly would be inefficient and produce unwanted by-products. Oxides are not liquids or gases (except CO₂), nor are they generally soluble.
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The activity (reactivity) series places hydrogen as a reference point. Metals above hydrogen (e.g., K, Na, Mg, Al, Zn, Fe) have a greater tendency to lose electrons (oxidize) than hydrogen does. When such a metal is placed in a dilute acid (like HCl or H₂SO₄), it donates electrons to H⁺ ions from the acid, reducing them to hydrogen gas (H₂). The metal itself dissolves to form a salt. Example: Zn(s) + 2HCl(aq) → ZnCl₂(aq) + H₂(g). Metals below hydrogen (Cu, Ag, Au) cannot displace hydrogen from acids.
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An amalgam is an alloy in which mercury (Hg) is one of the constituent metals. Mercury dissolves many other metals (like sodium, silver, gold, zinc, tin) to form pasty or liquid amalgams. Silver-tin amalgams are used in dental fillings. Sodium amalgam is used as a reducing agent in organic chemistry. Gold amalgam is used in gold extraction from ores. Solder (Pb+Sn), bronze (Cu+Sn), and brass (Cu+Zn) do not contain mercury. Amalgams are important because they allow mercury to be handled safely and used in various applications.
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Rusting of iron (formation of hydrated iron(III) oxide) can be prevented by various methods that cut off contact with oxygen and moisture. For an iron frying pan, multiple methods are applicable: painting (applying a coat of paint to create a barrier), oiling (greasing the surface to repel moisture), and galvanising (coating with zinc, though less common for frying pans due to toxicity concerns at high heat; but the question asks which method can prevent rusting, so it is theoretically valid). However, for a frying pan that is heated, seasoning with oil is common. The most accurate answer is “All of these” as all are valid rust prevention methods.
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Aluminium is used for cooking utensils primarily because it is lightweight, has good thermal conductivity, and forms a thin, adherent, protective oxide layer (Al₂O₃) on its surface. This oxide layer is inert and prevents the aluminium from reacting with food or corroding. While aluminium is also relatively cheap (compared to copper or stainless steel) and has a shiny appearance, the key reason it is safe for cooking is its oxide layer. Without this layer, aluminium would react with acidic foods. The oxide layer also prevents further oxidation.
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A displacement reaction (specifically a single displacement reaction) occurs when a more reactive element displaces a less reactive element from its compound. In the context of metals: Metal A (more reactive) + Compound of Metal B (less reactive) → Compound of Metal A + Metal B (displaced). For example: Fe + CuSO₄ → FeSO₄ + Cu. Iron (more reactive) displaces copper (less reactive). The other options describe combination reactions (metal + oxygen) or other types (metal + water), not displacement.
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Old copper vessels develop a green coating of basic copper carbonate [CuCO₃·Cu(OH)₂] due to corrosion. Acidic substances like lemon juice (citric acid) or tamarind (tartaric acid) clean the vessel by reacting with this green basic copper carbonate. The acid reacts with the carbonate to form soluble copper salts, carbon dioxide, and water, removing the green coating and exposing the shiny copper metal underneath. The acid does not react significantly with the copper metal itself because copper is below hydrogen in the reactivity series and does not displace hydrogen from acids easily.
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Brittleness is NOT a property of metals; it is a characteristic property of non-metals and some ionic compounds. Metals are generally malleable (can be hammered into sheets), ductile (can be drawn into wires), sonorous (produce a ringing sound when struck), and are good conductors of heat and electricity. Brittleness means the material breaks or shatters easily when subjected to stress, without significant deformation. Metals typically deform rather than shatter. Examples: Iron, copper, and aluminium are not brittle; they bend. Non-metals like sulfur and glass are brittle.
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Non-metals have high electronegativity, meaning they have a strong tendency to gain electrons to achieve a stable electronic configuration (octet). When a non-metal atom gains one or more electrons, it becomes a negatively charged ion called an anion. For example: Chlorine (Cl) gains 1 electron to form Cl⁻; Oxygen (O) gains 2 electrons to form O²⁻; Nitrogen (N) gains 3 electrons to form N³⁻. Metals form positive ions (cations) by losing electrons. Negative ions are characteristic of non-metals.
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Graphite is an allotrope of carbon, which is a non-metal. Unlike most non-metals, graphite is an excellent conductor of electricity. This is because of its unique structure: each carbon atom is bonded to three others in parallel hexagonal layers, leaving one free, delocalized electron per carbon atom. These delocalized electrons can move freely along the layers when a voltage is applied, making graphite conductive. Sulfur, phosphorus, and iodine are all non-conductors (insulators) as solids. Diamond (another carbon allotrope) is also an insulator.
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A displacement reaction occurs when a more reactive metal is added to a salt solution of a less reactive metal. In the reactivity series, aluminium (Al) is more reactive than magnesium (Mg)? No, let’s check: The order is K > Na > Ca > Mg > Al > Zn > Fe > Sn > Pb > H > Cu > Ag > Au. Actually, Mg is more reactive than Al (Mg is above Al). So Al cannot displace Mg from MgCl₂. Let’s re-evaluate: FeSO₄ + Ag: Ag is less reactive than Fe, so no displacement. ZnSO₄ + Zn: same metal, no reaction. NaCl + Cu: Cu is less reactive than Na, so no displacement. MgCl₂ + Al: Al is below Mg in reactivity? Actually, standard series: Mg is above Al. So Al cannot displace Mg. There seems to be an error. The correct pair that gives displacement would be, for example, Fe + CuSO₄. Among the options, none seem correct based on standard series. However, if the question intends Al to displace Mg? No. Possibly the intended answer is none, but since we must choose, check carefully: actually Al is less reactive than Mg, so no displacement. However, some series place Al above Mg? No, standard is Ca > Mg > Al. This is a trick. The correct answer should be that none work, but since the format requires one, and given common errors, the question might have a misprint. For the purpose of this exercise, we note that a displacement reaction requires a more reactive metal displacing a less reactive one. Mg is above Al, so Al cannot displace Mg.
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Sodium (Na) is an alkali metal at the top of the reactivity series. It reacts extremely vigorously with cold water, producing sodium hydroxide and hydrogen gas, with the evolution of so much heat that the hydrogen catches fire. The reaction is: 2Na + 2H₂O → 2NaOH + H₂ + Heat. Iron reacts slowly with steam, not with cold water. Copper and silver do not react with water at all. Potassium is even more reactive than sodium, but among the given options, sodium is the correct answer.
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Sodium and potassium are extremely reactive metals. They react spontaneously with oxygen and water vapor present in the air, generating enough heat to catch fire. Storing them under kerosene or mineral oil serves as a physical barrier, cutting off contact with both air (oxygen) and moisture. This prevents accidental fires and ensures safe storage. While they are also soft and have low melting points, these are not the reasons for storing under oil. The primary reason is to prevent violent reactions with air and moisture.
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Non-metals are generally brittle in the solid state, meaning they break or shatter easily when hammered or subjected to stress. For example, sulfur, phosphorus, and iodine are brittle solids. They are not sonorous (do not produce a ringing sound); they are not malleable (cannot be hammered into sheets); and they are not ductile (cannot be drawn into wires). These opposite properties (malleability, ductility, sonority) are characteristic of metals. Graphite is a non-metal that is an exception (it is soft and slippery, but still not malleable/ductile in the metallic sense).
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Only metals that are above hydrogen in the reactivity series can displace hydrogen from dilute acids. Metals below hydrogen cannot. Copper (Cu) is below hydrogen in the reactivity series. Therefore, copper does not react with dilute hydrochloric acid or dilute sulfuric acid to produce hydrogen gas. Magnesium, zinc, and iron are all above hydrogen and will displace hydrogen from acids (though at different rates). The reaction for a metal above hydrogen is: Metal + Acid → Salt + H₂. Copper shows no such reaction.
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Rusting is the corrosion of iron to form hydrated iron(III) oxide (Fe₂O₃·xH₂O). For rusting to occur, both oxygen (from air) and water (or moisture) must be present simultaneously. The overall reaction involves iron reacting with oxygen in the presence of water. If either oxygen or water is absent, rusting does not occur. For example, iron does not rust in dry air (no water) or in deoxygenated water (no oxygen). Oil prevents rust by creating a barrier that excludes both air and water. Therefore, both air (oxygen) and water are essential.
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Metals have low electronegativity and low ionization energy, meaning they have a strong tendency to lose electrons from their valence shell to achieve a stable electronic configuration (octet). When a metal atom loses one or more electrons, it becomes a positively charged ion called a cation. For example: Sodium (Na) loses 1 electron to form Na⁺; Magnesium (Mg) loses 2 electrons to form Mg²⁺; Aluminium (Al) loses 3 electrons to form Al³⁺. Non-metals form negative ions (anions) by gaining electrons.
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Galvanisation is the process of applying a protective zinc coating to iron or steel to prevent rusting. Zinc is more reactive than iron, so it acts as a sacrificial anode. Even if the zinc coating is scratched, the zinc corrodes preferentially, protecting the iron underneath. Zinc also forms a durable, adherent zinc oxide layer. Coating with tin is called “tinning” (used for tin cans). Copper coating is copper plating; aluminium coating is aluminising. Galvanisation specifically refers to zinc coating.
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Tarnished copper vessels develop a green coating of basic copper carbonate [CuCO₃·Cu(OH)₂]. Lemon juice contains citric acid, which is acidic. The acid reacts with the basic copper carbonate in a neutralization reaction, dissolving the green coating and forming soluble copper citrate, carbon dioxide, and water. This removes the tarnish and exposes the shiny copper metal underneath. The acid does not significantly react with the copper metal itself because copper is below hydrogen in the reactivity series and does not displace hydrogen from weak acids easily.
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Food cans (tin cans) are coated with tin, not zinc, because zinc is more reactive than tin. If zinc were used, it could react with the acidic contents of the food (e.g., tomato sauce, fruits) and contaminate the food with toxic zinc compounds. Tin is less reactive than zinc and more resistant to attack by food acids. Additionally, tin is non-toxic and safe for food contact. While tin is costlier, the primary reason is chemical safety. Zinc’s higher reactivity makes it unsuitable for direct food contact containers.
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Metals at the bottom of the reactivity series (such as gold, platinum, silver, and copper) are least reactive and do not corrode easily. They are often called noble metals. These metals have very high reduction potentials and a low tendency to lose electrons, making them resistant to reactions with oxygen, water, and most acids. In contrast, metals at the top of the series (e.g., K, Na, Ca, Mg) are highly reactive and corrode very easily. Metals in the middle (e.g., Zn, Fe, Pb) are moderately reactive and corrode under certain conditions.
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The activity series (also called reactivity series) is a list of metals arranged in order of their decreasing chemical reactivity. The most reactive metal (potassium) is placed at the top, and the least reactive metal (gold) is placed at the bottom. This arrangement allows chemists to predict the behaviour of metals, such as their reaction with water, acids, oxygen, and their ability to displace other metals from compound solutions. Alphabetical order, atomic mass, or density do not correlate with chemical reactivity.
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Metals occur in nature both in the free (native) state and in the combined state (as compounds). The state depends on their reactivity. Less reactive metals (bottom of series: gold, silver, platinum, copper) are found in the free state because they do not react easily with oxygen, moisture, and other elements. Highly reactive metals (top of series: sodium, potassium, calcium, magnesium, aluminium) are never found free; they always occur as compounds (oxides, chlorides, carbonates, silicates). Moderately reactive metals (zinc, iron, lead) occur primarily in combined form but sometimes in free state.
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Silver and gold are noble metals located at the bottom of the reactivity series. They have very high reduction potentials and are chemically very unreactive. Gold does not corrode at all; it remains pure and lustrous for centuries. Silver tarnishes slowly (forms black Ag₂S due to H₂S in air), but this is a surface reaction, not deep corrosion like rusting. In contrast, sodium and potassium react violently with air; iron and zinc corrode readily (iron rusts, zinc tarnishes); aluminium and magnesium are reactive but form protective oxide layers, though they can corrode under certain conditions.
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An alloy is a homogeneous mixture (solid solution) of two or more metals, or a metal and a non-metal. The constituent elements are uniformly distributed at the atomic level, giving the alloy a single-phase structure. Alloys are not chemical compounds because they do not have fixed stoichiometric ratios; the proportions of the components can vary. They are also not heterogeneous mixtures because the components cannot be seen separately. Examples: brass (Cu + Zn), bronze (Cu + Sn), steel (Fe + C). Alloys often have properties superior to their constituent elements.
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Non-metals do not displace hydrogen from dilute acids. This is because non-metals are generally electron acceptors (they gain electrons to form negative ions) and cannot donate electrons to H⁺ ions to reduce them to H₂. In contrast, metals above hydrogen in the reactivity series can displace hydrogen from dilute acids. Non-metals may react with water (e.g., chlorine) or with oxygen (e.g., sulfur burning), but they do not produce hydrogen by displacement from acids. For a displacement reaction to produce hydrogen, the element must be a stronger reducing agent than hydrogen.
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An amphoteric oxide is one that can react with both acids and bases to form salt and water. Aluminium oxide (Al₂O₃) is the classic example of an amphoteric oxide. It reacts with hydrochloric acid (acid) to form aluminium chloride and water (basic behaviour), and it reacts with sodium hydroxide (base) to form sodium aluminate and water (acidic behaviour). Na₂O and MgO are basic oxides (react only with acids). CO₂ is an acidic oxide (reacts only with bases). Thus, Al₂O₃ is amphoteric.
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Silver (Ag) has the highest electrical conductivity of all known metals. It is the benchmark for conductivity (often set at 100% IACS – International Annealed Copper Standard). Silver is followed very closely by copper. However, silver is expensive and tarnishes (though tarnish does not greatly affect conductivity). Copper is more commonly used for electrical wiring due to its high conductivity and lower cost. Aluminium is also a good conductor (about 61% of silver) and is used for overhead power lines. Iron and lead have much lower conductivity. The best conductor is silver.
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Calcination is the process of heating an ore (typically a carbonate or hydroxide ore) strongly in a limited supply of air or in the absence of air. The purpose is to decompose the ore into a metal oxide and to remove volatile impurities (like carbon dioxide, water vapour). For example: ZnCO₃ → ZnO + CO₂. Roasting is heating a sulphide ore in excess air. Smelting involves heating the ore with a reducing agent to extract the metal. Refining is the purification of the extracted metal. Calcination specifically occurs in limited/absence of air.
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Noble metals are metals that are resistant to corrosion and oxidation in moist air (unlike most base metals). They are located at the bottom of the reactivity series. Platinum (Pt) is a classic noble metal. Other noble metals include gold (Au), silver (Ag), ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium (Ir). Copper, zinc, and iron are not considered noble metals because they corrode or tarnish under environmental conditions (copper forms a green patina, zinc tarnishes, iron rusts). Platinum is highly unreactive and does not corrode easily.Close