Comprehensive Study Guide on Metals and Non-Metals

Physical Properties and Exceptions of Metals and Non-Metals

• Physical Properties of Metals:

  • Mechanical Strength: Metals are hard and exhibit high tensile strength.

  • Physical State: Metals exist as solids at room temperature.

  • Acoustic Property: Metals are sonorous, producing a deep ringing sound when struck.

  • Conductivity: Metals are good conductors of both heat and electricity.

  • Malleability: Metals are malleable, meaning they can be hammered or beaten into thin sheets.

  • Ductility: Metals are ductile, meaning they can be drawn into thin wires.

  • Thermal Transitions: Metals generally possess high melting points and high boiling points.

  • Density: Metals are dense materials.

  • Highest density metal: Osmium ($\text{Os}$

  • Least density metal: Lithium ($\text{Li}$

  • Lustre: Metals possess a characteristic metallic lustre (shiny surface).

  • Appearance: Metals are typically silver-grey in colour.

• Physical Properties of Non-Metals:

  • Definition: Nonmetals are defined as elements that do not exhibit the properties of metals.

  • Physical States: Non-metals occur in all three physical states at room temperature: solids, liquids, and gases.

  • Brittleness: Solid non-metals are brittle and break easily under stress.

  • Mechanical Inability: Non-metals are non-malleable and non-ductile.

  • Acoustics: Non-metals are non-sonorous.

  • Conductivity: Non-metals are bad conductors of heat and electricity.

• Exceptions to Physical Properties:

  • Hardness in Metals: Alkali metals ($\text{Na}$, $\text{K}$, $\text{Li}$) are soft and can be cut easily using a knife.

  • Solid State in Metals: Mercury ($\text{Hg}$) is a liquid at room temperature.

  • Thermal Conductivity in Metals: Lead ($\text{Pb}$) and mercury ($\text{Hg}$) are poor conductors of heat.

  • Thermal Expansion: Mercury ($\text{Hg}$) expands significantly upon even the slightest change in temperature.

  • Melting Points in Metals: Gallium ($\text{Ga}$) and caesium ($\text{Cs}$) possess very low melting points and will melt even in the palm of a hand.

  • Metallic Colour: Gold ($\text{Au}$) and copper ($\text{Cu}$) deviate from the typical silver-grey colouration.

  • Lustre in Non-Metals: Iodine ($\text{I}$) is a non-metal that possesses a distinct metallic lustre.

  • Electrical Conductivity in Non-Metals: Carbon in the allotropic form of graphite conducts electricity.

  • Thermal Conductivity and Melting Point in Non-Metals: Carbon in the allotropic form of diamond conducts heat exceptionally well and possesses an extremely high melting point.

Chemical Properties and Reactions of Metals with Oxygen

• General Chemical Trends of Metals:

  • Highly reactive alkali metals ($\text{Li}$, $\text{Na}$, $\text{K}$, etc.) react vigorously with water, oxygen, and atmospheric air.

  • Magnesium ($\text{Mg}$) reacts with hot water.

  • Aluminium ($\text{Al}$), iron ($\text{Fe}$), and zinc ($\text{Zn}$) do not react with cold or hot water, reacting only with steam.

  • Unreactive metals such as copper ($\text{Cu}$), silver ($\text{Ag}$), platinum ($\text{Pt}$), and gold ($\text{Au}$) do not react with water or dilute acids.

• Reaction of Metals with Oxygen (Combustion in Air):

  • General Transformation:     $\text{Metal} + \text{Oxygen} \rightarrow \text{Metal oxide (basic)}$

  • Alkali Metals Storage: Sodium ($\text{Na}$) and potassium ($\text{K}$) react vigorously with atmospheric oxygen and moisture, easily catching fire; therefore, they are kept permanently immersed under kerosene oil.     $4\text{K}(s) + \text{O}_2(g) \rightarrow 2\text{K}_2\text{O}(s)$

  • Protective Oxide Layer Formation: Magnesium ($\text{Mg}$), aluminium ($\text{Al}$), zinc ($\text{Zn}$), and lead ($\text{Pb}$) react slowly with oxygen in air to develop a thin, protective surface oxide coating that prevents further internal corrosion.

  • Combustion of Magnesium: Magnesium burns brightly upon heating:     $2\text{Mg}(s) + \text{O}_2(g) \rightarrow 2\text{MgO}(s)$

  • Combustion observation: $\text{Mg}$ burns with an intense, dazzling white light.

  • Oxidation of Aluminium:     $4\text{Al}(s) + 3\text{O}_2(g) \rightarrow 2\text{Al}_2\text{O}_3(s)$

  • Noble Metal Inactivity: Silver ($\text{Ag}$), platinum ($\text{Pt}$), and gold ($\text{Au}$) do not burn or react with oxygen even at elevated temperatures.

• Basic Metal Oxides:

  • Most metal oxides are basic in nature. Certain basic metal oxides dissolve in water to produce soluble bases known as alkalis, turning red litmus indicator paper blue:     $\text{Na}_2\text{O}(s) + \text{H}_2\text{O}(l) \rightarrow 2\text{NaOH}(aq)$     $\text{K}_2\text{O}(s) + \text{H}_2\text{O}(l) \rightarrow 2\text{KOH}(aq)$

• Amphoteric Oxides of Metals:

  • Definition: Amphoteric oxides are metal oxides that react with both acids and bases to yield salt and water.

  • Examples: Aluminium oxide ($\text{Al}_2\text{O}_3$ / $\text{Al}_2\text{O}_4$), zinc oxide ($\text{ZnO}$), lead oxide ($\text{PbO}$), and tin oxide ($\text{SnO}$).

  • Reactions of Aluminium Oxide ($\text{Al}_2\text{O}_3$):

  • Reaction with Acid:       $\text{Al}_2\text{O}_3(s) + 6\text{HCl}(aq) \rightarrow 2\text{AlCl}_3(aq) + 3\text{H}_2\text{O}(l)$

  • Reaction with Base:       $\text{Al}_2\text{O}_3(s) + 2\text{NaOH}(aq) \rightarrow 2\text{NaAlO}_2(aq) + \text{H}_2\text{O}(l)$

  • Reactions of Zinc Oxide ($\text{ZnO}$):

  • Reaction with Acid:       $\text{ZnO}(s) + 2\text{HCl}(aq) \rightarrow \text{ZnCl}_2(aq) + \text{H}_2\text{O}(l)$

  • Reaction with Base:       $\text{ZnO}(s) + 2\text{NaOH}(aq) \rightarrow \text{Na}_2\text{ZnO}_2(aq) + \text{H}_2\text{O}(l)$

Reactivity Series and Reactions with Water

• The Reactivity Series:

  • The reactivity series ranks metals in descending order of chemical reactivity, arranged from highest reactivity to lowest reactivity:

  • Potassium ($\text{K}$) — Highly Active Metal

  • Barium ($\text{Ba}$)

  • Calcium ($\text{Ca}$)

  • Sodium ($\text{Na}$)

  • Magnesium ($\text{Mg}$)

  • Aluminium ($\text{Al}$)

  • Zinc ($\text{Zn}$)

  • Iron ($\text{Fe}$)

  • Nickel ($\text{Ni}$)

  • Tin ($\text{Sn}$)

  • Lead ($\text{Pb}$)

  • Hydrogen ($\text{H}$)

  • Copper ($\text{Cu}$)

  • Mercury ($\text{Hg}$)

  • Silver ($\text{Ag}$)

  • Gold ($\text{Au}$)

  • Platinum ($\text{Pt}$)

• Reactions of Metals with Water or Steam:

  • General Scheme:     $\text{Metal} + \text{Water} \rightarrow \text{Metal hydroxide or Metal oxide} + \text{Hydrogen}$

  • Reactions with Cold Water:

  • Sodium reacts violently with cold water, producing exothermic heat that ignites the liberated hydrogen gas:       $2\text{Na} + 2\text{H}_2\text{O}\text{ (cold)} \rightarrow 2\text{NaOH} + \text{H}_2 + \text{heat}$

  • Calcium reacts less violently with cold water:       $\text{Ca} + 2\text{H}_2\text{O}\text{ (cold)} \rightarrow \text{Ca(OH)}_2 + \text{H}_2$

  • Reactions with Hot Water:

  • Magnesium does not react with cold water but reacts with hot water to produce magnesium hydroxide and hydrogen:       $\text{Mg} + 2\text{H}_2\text{O}\text{ (hot)} \rightarrow \text{Mg(OH)}_2 + \text{H}_2$

  • Reactions with Steam:

  • Aluminium, zinc, and iron react exclusively with steam to produce metal oxides rather than hydroxides:       $2\text{Al} + 3\text{H}_2\text{O}\text{ (steam)} \rightarrow \text{Al}_2\text{O}_3 + 3\text{H}_2$       $\text{Zn} + \text{H}_2\text{O}\text{ (steam)} \rightarrow \text{ZnO} + \text{H}_2$       $3\text{Fe} + 4\text{H}_2\text{O}\text{ (steam)} \rightarrow \text{Fe}_3\text{O}_4 + 4\text{H}_2$

Reactions with Acids and Alkalis

• Reactions of Metals with Dilute Mineral Acids:

  • General Principle:     $\text{Metal} + \text{dilute acid} \rightarrow \text{Salt} + \text{Hydrogen gas}$

  • Hydrochloric Acid Reaction:     $2\text{Na}(s) + 2\text{HCl}\text{ (dilute)} \rightarrow 2\text{NaCl}(aq) + \text{H}_2(g)$

  • Sulphuric Acid Reaction:     $2\text{K}(s) + \text{H}_2\text{SO}_4\text{ (dilute)} \rightarrow \text{K}_2\text{SO}_4(aq) + \text{H}_2(g)$

  • Special Behavior with Nitric Acid ($\text{HNO}_3$):

  • Hydrogen gas is typically not liberated when metals react with nitric acid because $\text{HNO}_3$ acts as a powerful oxidising agent.

  • Only magnesium ($\text{Mg}$) and manganese ($\text{Mn}$) react with extremely dilute nitric acid to liberate hydrogen gas:       $\text{Mg}(s) + 2\text{HNO}_3\text{ (dilute)} \rightarrow \text{Mg(NO}_3)_2(aq) + \text{H}_2(g)$       $\text{Mn}(s) + 2\text{HNO}_3\text{ (dilute)} \rightarrow \text{Mn(NO}_3)_2(aq) + \text{H}_2(g)$

• Reactions of Metals with Alkalis (Bases):

  • General Scheme:     $\text{Base} + \text{metal} \rightarrow \text{salt} + \text{hydrogen}$

  • Reaction of Zinc with Sodium Hydroxide:     $2\text{NaOH}(aq) + \text{Zn}(s) \rightarrow \text{Na}_2\text{ZnO}_2(aq) + \text{H}_2(g)$

  • The formed salt is sodium zincate ($\text{Na}_2\text{ZnO}_2$).

  • Reaction of Aluminium with Sodium Hydroxide:     $2\text{NaOH}(aq) + 2\text{Al}(s) + 2\text{H}_2\text{O}(l) \rightarrow 2\text{NaAlO}_2(aq) + 2\text{H}_2(g)$

  • The formed salt is sodium aluminate ($\text{NaAlO}_2$).

Displacement Reactions and Occurrence of Metals

• Displacement Reactions:

  • Definition: A chemical process where a more reactive element displaces a less reactive element from its aqueous salt solution or compound.

  • General Form:     $\text{Metal A} + \text{Salt of metal B} \rightarrow \text{Salt of metal A} + \text{Metal B}$

  • Displacement of Copper by Iron:     $\text{Fe}(s) + \text{CuSO}_4(aq) \rightarrow \text{FeSO}_4(aq) + \text{Cu}(s)$

  • Displacement of Silver by Copper:     $\text{Cu}(s) + 2\text{AgNO}_3(aq) \rightarrow \text{Cu(NO}_3)_2(aq) + 2\text{Ag}(s)$

• Industrial Applications of Displacement Reactions:

  • Metal Extraction: Utilizing displacement processes for the chemical reduction and extraction of metals from ores.

  • Steel Manufacturing: Utilized within metallurgical processes for producing steel alloys.

  • The Thermite Reaction:

  • The highly exothermic displacement reduction of ferric oxide using aluminium powder:       $\text{Al}(s) + \text{Fe}_2\text{O}_3(s) \rightarrow \text{Al}_2\text{O}_3 + \text{Fe}\text{ (molten)}$

  • Application: The molten iron produced is utilized on-site for welding broken railway tracks and repairing heavily cracked machine components.

• Occurrence and Classification of Metals in Nature:

  • Combined State (Minerals): Most elements, particularly metals, naturally occur in a chemically combined state associated with other elements. All such naturally occurring inorganic compounds are classified as minerals.

  • Viable Extraction (Ores): Only a select group of minerals contain a sufficiently high percentage of metal that makes industrial and economical extraction commercially viable; these viable mineral sources are designated as ores.

  • Native or Free State: The least reactive, uncombined noble metals—specifically gold ($\text{Au}$) and platinum ($\text{Pt}$)—occur naturally in their native, uncombined elementary metallic state.

Corrosion Mechanisms and Prevention Strategies

• Corrosion Dynamics:

  • Definition: The gradual deterioration and breakdown of a material, primarily a metal, caused by spontaneous chemical or electrochemical reactions with moisture, atmospheric oxygen, or airborne chemical contaminants in the surrounding environment.

• Corrosion Reactions in Everyday Metals:

  • Rusting of Iron:

  • Requires simultaneous exposure to atmospheric oxygen and water:       $4\text{Fe}(s) + 3\text{O}_2\text{ (from air)} + x\text{H}_2\text{O}\text{ (moisture)} \rightarrow 2\text{Fe}_2\text{O}_3 \cdot x\text{H}_2\text{O}\text{ (rust)}$

  • Corrosion of Copper:

  • Copper reacts over prolonged periods with moist carbon dioxide in the atmosphere, creating a distinct basic green patina surface layer composed of basic copper carbonate:       $\text{Cu}(s) + \text{H}_2\text{O}\text{ (moisture)} + \text{CO}_2\text{ (from air)} \rightarrow \text{CuCO}_3 \cdot \text{Cu(OH)}_2\text{ (green)}$

  • Tarnishing of Silver:

  • Silver articles react slowly with trace airborne hydrogen sulphide ($\text{H}_2\text{S}$), developing a black surface tarnish layer of silver sulphide:       $\text{Ag}(s) + \text{H}_2\text{S}\text{ (from air)} \rightarrow \text{Ag}_2\text{S}\text{ (black)} + \text{H}_2(g)$

• Methods for Prevention of Corrosion:

  • Surface Barrier Coatings: Application of grease, oil, or paints over clean metal surfaces creates an impermeable physical barrier that keeps ambient air and moisture from contacting the metal.

  • Alloying: Forming metallic alloys alters the bulk chemical composition, imparting strong resistance against corrosive environmental attacks (e.g., stainless steel).

  • Galvanization: Iron articles are submerged in and coated with a protective layer of molten zinc ($\text{Zn}$), isolating the underlying iron from environmental moisture.

  • Electroplating: Electrolytic deposition of a protective coating of a non-corrosive metal onto another metallic object using direct electric current; this method simultaneously provides corrosion resistance and enhances the metallic appearance (e.g., nickel plating and silver plating).

  • Sacrificial Protection: Magnesium is more electrochemically reactive than iron. When magnesium is placed in electrical contact with or coated onto iron and steel articles, it functions as the cathode, preferentially undergoing oxidation and reaction (sacrificing itself) instead of the iron, thereby preserving the structural integrity of the steel article.

Characteristics and Compositions of Alloys

• Nature of Alloys:

  • Definition: Alloys are uniform, homogeneous mixtures consisting of a metal combined with one or more other metals or non-metals.

  • Purpose of Alloying: Alloying fundamentally alters and enhances specific desirable physical and mechanical properties, significantly increasing hardness, tensile strength, and chemical resistance to oxidative corrosion.

• Representative Alloy Compositions:

  • Brass: An alloy composed of copper ($\text{Cu}$) and zinc ($\text{Zn}$).

  • Bronze: An alloy composed of copper ($\text{Cu}$) and tin ($\text{Sn}$).

  • Solder: A low-melting-point alloy composed of lead ($\text{Pb}$) and tin ($\text{Sn}$).

  • Amalgam: Any specialized alloy formed by combining mercury ($\text{Hg}$) with another metal.