Comprehensive Study Notes: Chapter 3 - Metals and Nonmetals

Classification of Elements

Everything around us is composed of elements.
Elements are classified into two main categories based on their physical and chemical properties: Metals and Non-metals.
Distribution: Nearly $75\%$ of all known elements are classified as metals, while the remaining elements are non-metals.

Examples of Metals:

Iron ( $Fe$ )
Copper ( $Cu$ )
Aluminium ( $Al$ )
Zinc ( $Zn$ )
Gold ( $Au$ )
Silver ( $Ag$ )

Examples of Non-Metals:

Oxygen ( $O$ )
Nitrogen ( $N$ )
Sulphur ( $S$ )
Carbon ( $C$ )
Phosphorus ( $P$ )
Chlorine ( $Cl$ )

Physical Properties of Metals

Lustre: Metals possess a shiny surface, a property known as metallic lustre.
Hardness: Most metals are characterized by being hard.
Malleability: This is the property by which metals can be beaten into thin sheets. Gold is the most malleable metal.
Ductility: This is the property of metals by which they can be drawn into thin wires. Gold is the most ductile metal.
Conductivity: Metals are efficient conductors of both heat and electricity. Silver is the best conductor of electricity.
Sonority: Metals produce a distinct ringing sound when struck, a property called sonority.
Melting and Boiling Points: Most metals possess high melting and boiling points.
Density: Most metals possess high density.

Exceptions in Physical Properties:

State: Mercury ( $Hg$ ) is the only metal that exists as a liquid at room temperature.
Melting Point: Gallium ( $Ga$ ) and Cesium ( $Cs$ ) have very low melting points and will melt if held on the palm of the hand.
Hardness: Sodium ( $Na$ ), Potassium ( $K$ ), and Lithium ( $Li$ ) are soft alkali metals that can be easily cut with a knife.
Non-metal Lustre: Iodine is a non-metal that possesses lustre (shiny surface).
Non-metal Conductivity: Graphite, an allotrope of carbon, is a non-metal that conducts electricity.
Hardness (Non-metal): Diamond, an allotrope of carbon, is the hardest natural substance known.

Comparative Summary of Metals and Non-Metals

Lustrous: Metals are lustrous; non-metals are generally dull.
Malleability: Metals are malleable; non-metals are brittle.
Ductility: Metals are ductile; non-metals are non-ductile.
Sonority: Metals are sonorous; non-metals are non-sonorous.
Conductivity: Metals are good conductors; non-metals are poor conductors (except graphite).
Hardness: Metals are usually hard; non-metals are usually soft (except diamond).
Density: Metals have high density; non-metals have low density.
Melting Point: Metals have high melting points; non-metals have low melting points (except diamond).

Allotropes of Carbon

Carbon is an exceptional non-metal that exists in different structural forms called allotropes. Allotropes share the same chemical identity but differ in physical properties.

1. Diamond

Hardest natural substance known.
Features an extremely high melting point and boiling point.
Does not conduct electricity.
Uses: Used in cutting tools and jewelry.

2. Graphite

Characterized as being soft and slippery.
An excellent conductor of electricity.
Uses: Used in electrodes, dry cells, and pencil leads.

Chemical Properties: Reaction of Metals with Oxygen

Metals react with oxygen to produce metal oxides.
General Equation: $\text{Metal} + \text{Oxygen} \rightarrow \text{Metal Oxide}$
Nature: Metal oxides are generally basic in nature.

Specific Examples:

Magnesium: When magnesium burns in air, it produces a dazzling white flame and forms a white ash.
- $2Mg + O_2 \rightarrow 2MgO$
Copper: Copper does not burn but forms a black coating of copper(II) oxide when heated.
- $2Cu + O_2 \rightarrow 2CuO$
Aluminium: Reacts with oxygen to form a thin protective layer.
- $4Al + 3O_2 \rightarrow 2Al_2O_3$

Protective Oxide Layers:

Metals like Magnesium ( $Mg$ ), Aluminium ( $Al$ ), Zinc ( $Zn$ ), and Lead ( $Pb$ ) form a thin, stable oxide layer on their surface.
This layer acts as a shield, preventing further oxidation and protecting the metal from corrosion.

Combustion of Iron:

Bulk iron pieces do not burn upon heating.
Iron filings burn vigorously when sprinkled into a flame because their larger surface area facilitates the reaction.
$3Fe + 2O_2 \rightarrow Fe_3O_4$

Amphoteric Oxides

Most metal oxides are basic (e.g., $MgO + H_2O \rightarrow Mg(OH)_2$ , which is a base).
Amphoteric Oxides are specific metal oxides that exhibit both acidic and basic behavior, reacting with both acids and bases to produce salt and water.
Examples: Aluminium oxide ( $Al_2O_3$ ) and Zinc oxide ( $ZnO$ ).

Reactions of Aluminium Oxide ( $Al_2O_3$ ):

With Acid: $Al_2O_3 + 6HCl \rightarrow 2AlCl_3 + 3H_2O$
With Base: $Al_2O_3 + 2NaOH \rightarrow 2NaAlO_2 + H_2O$ (Product: Sodium Aluminate).

Reaction of Metals with Water

Different metals react with water at varying rates based on their reactivity.

(a) Reaction with Cold Water:

Potassium ( $K$ ) and Sodium ( $Na$ ): React violently and highly vigorously. The reaction is so exothermic that the evolved hydrogen gas catches fire immediately.
- $2K + 2H_2O \rightarrow 2KOH + H_2$
- $2Na + 2H_2O \rightarrow 2NaOH + H_2$
Storage: Sodium and potassium are stored under kerosene to prevent accidental reactions with air and moisture.
Calcium ( $Ca$ ): The reaction is less vigorous. Calcium starts floating because bubbles of hydrogen gas stick to its surface.
- $Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2$

(b) Reaction with Hot Water:

Magnesium ( $Mg$ ): Does not react with cold water; it reacts slowly with hot water to form magnesium hydroxide and hydrogen.
- $Mg + 2H_2O \rightarrow Mg(OH)_2 + H_2$

(c) Reaction with Steam:

Metals like Aluminium ( $Al$ ), Zinc ( $Zn$ ), and Iron ( $Fe$ ) only react with steam.
- $Zn + H_2O \text{ (steam)} \rightarrow ZnO + H_2$
- $3Fe + 4H_2O \text{ (steam)} \rightarrow Fe_3O_4 + 4H_2$

(d) No Reaction with Water:

Copper ( $Cu$ ), Silver ( $Ag$ ), Gold ( $Au$ ), and Platinum ( $Pt$ ) are the least reactive metals and do not react with water or steam at all.

Reaction of Metals with Acids

Metals typically react with dilute acids to produce a salt and hydrogen gas.
General Equation: $\text{Metal} + \text{Dilute Acid} \rightarrow \text{Salt} + H_2$
Examples:
- $Zn + 2HCl \rightarrow ZnCl_2 + H_2$
- $Mg + H_2SO_4 \rightarrow MgSO_4 + H_2$
Test for Hydrogen: When a burning splint is brought near the gas, it burns with a characteristic 'pop' sound.
Non-reactive Metals: Copper ( $Cu$ ), Silver ( $Ag$ ), Gold ( $Au$ ), and Platinum ( $Pt$ ) do not react with dilute acids because they are less reactive than hydrogen.

The Nitric Acid ( $HNO_3$ ) Exception:

Nitric acid normally does not produce hydrogen gas when reacting with metals.
It is a strong oxidizing agent that oxidizes the produced hydrogen into water ( $H_2O$ ) while the acid itself is reduced to nitrogen oxides ( $NO$ , $NO_2$ , or $N_2O$ ).
Exceptions: Very dilute nitric acid reacts with Magnesium ( $Mg$ ) and Manganese ( $Mn$ ) to evolve hydrogen gas.

Displacement Reactions

A displacement reaction occurs when a more reactive metal displaces a less reactive metal from its salt solution.
Example 1: $Zn + CuSO_4 \rightarrow ZnSO_4 + Cu$
- Observation: The blue color of the copper sulphate solution fades, and brown copper is deposited.
Example 2: $Fe + CuSO_4 \rightarrow FeSO_4 + Cu$
- Observation: The blue solution turns green, and copper is deposited.
Example 3: $Cu + AgNO_3 \rightarrow Cu(NO_3)_2 + 2Ag$
- Observation: Silver crystals are deposited.
No Reaction: $Cu + ZnSO_4 \rightarrow \text{No reaction}$ (because Copper is less reactive than Zinc).

The Reactivity Series

The reactivity series is the arrangement of metals in decreasing order of their chemical reactivity.

K (Potassium) - Most Reactive
Na (Sodium)
Ca (Calcium)
Mg (Magnesium)
Al (Aluminium)
Zn (Zinc)
Fe (Iron)
Pb (Lead)
H (Hydrogen) - Reference element
Cu (Copper)
Hg (Mercury)
Ag (Silver)
Au (Gold)
Pt (Platinum) - Least Reactive

Memory Tip: "Please Stop Calling Me A Zebra Instead Try Learning How Copper Saves Gold Platinum"

Ionic Compounds

Ionic compounds (or electrovalent compounds) are formed by the transfer of electrons from a metal to a non-metal.

Formation of Sodium Chloride ( $NaCl$ ):

Sodium ( $Na$ ): Loses one electron to achieve stability ( $Na \rightarrow Na^+ + e^-$ ).
Chlorine ( $Cl$ ): Gains one electron ( $Cl + e^- \rightarrow Cl^-$ ).
Bonding: The attraction between the positive sodium ion and negative chloride ion forms the compound ( $Na^+ + Cl^- \rightarrow NaCl$ ).

Formation of Aluminium Chloride ( $AlCl_3$ ):

Involves the transfer of electrons from aluminium to chlorine atoms.

Characteristics of Ionic Compounds:

Solid and Hard: They are hard solids due to strong electrostatic forces of attraction between ions.
Melting and Boiling Points: They possess very high melting and boiling points because a significant amount of energy is required to break the strong inter-ionic attraction.
Solubility: They are generally soluble in water but insoluble in organic solvents (like kerosene or petrol).
Electrical Conductivity: They conduct electricity in the molten state or when dissolved in an aqueous solution (where ions are free to move). They do not conduct electricity in solid state because ions are held in fixed positions.

Anodising

Anodising is a process used to form a thick, protective layer of aluminium oxide ( $Al_2O_3$ ) on the surface of aluminium via electrolysis.

The Process:

A clean aluminium article serves as the anode (positive electrode).
Dilute sulphuric acid ( $H_2SO_4$ ) is used as the electrolyte.
Oxygen gas is produced at the anode during electrolysis.
The oxygen reacts with the aluminium anode to create a thick, hard, and protective oxide coating.

Advantages and Applications:

Advantages: Prevents corrosion, increases durability, provides scratch resistance, and the layer can be dyed in various colors for an attractive finish.
Applications: Used in cooking utensils, window frames, doors, aircraft parts, electronic device casings, and decorative items.

Aqua Regia (Royal Water)

Definition: A freshly prepared mixture of concentrated Hydrochloric Acid ( $HCl$ ) and concentrated Nitric Acid ( $HNO_3$ ).
Ratio: Prepared in a volume ratio of $3 : 1$ ( $HCl : HNO_3$ ).
Properties:
- Highly corrosive and fuming liquid.
- A powerful oxidizing and dissolving agent.
Function: It can dissolve noble metals like Gold ( $Au$ ) and Platinum ( $Pt$ ). This is possible because the reaction produces highly reactive chlorine ( $Cl_2$ ) and Nitrosyl chloride ( $NOCl$ ).