Chemistry of Main Group Elements: Detailed Notes

Group 1 Elements (Alkali Metals)

Key points:

• General characteristics and trends:

  • Highly reactive metals, most electropositive elements
  • Low ionization energies, large atomic radii
  • Silvery-white appearance, soft, low melting and boiling points
  • Abundance: sodium most abundant, francium least

• Reactivity and reducing power:

  • React vigorously with water, forming hydroxides and liberating hydrogen gas
  • Highly reducing agents, easily lose valence electron to form stable cations

• Alkali metal hydroxides:

  • Strong bases, soluble in water, high electrical conductivity
  • Used in various industries, e.g. soap, paper, and textile manufacturing

• Alkali metal halides:

  • Ionic compounds, mostly colorless and soluble in water
  • Solubility decreases down the group, lithium fluoride least soluble
  • Used as sources of respective alkali metals, in photography, and as fluxes

• Applications:

  • Sodium: table salt, production of various compounds, street lights
  • Potassium: fertilizers, explosives, medicine (electrolytes)
  • Rubidium and Cesium: atomic clocks, electronics

Relevant NCERT references (Class 11):

• Chapter 10, The s-Block Elements
• Section 10.1, General Introduction
• Section 10.2, Electronic Configuration
• Section 10.3, Physical Properties

Group 2 Elements (Alkaline Earth Metals)

Key points:

• General characteristics and trends:

  • Less reactive than alkali metals, lower reducing power
  • Moderate ionization energies, larger atomic radii than alkali metals
  • Silvery-white appearance, harder than alkali metals
  • Abundance: calcium most abundant, radium least

• Reactivity and reducing power:

  • React with water, forming hydroxides and liberating hydrogen gas, but less vigorous than alkali metals

• Alkaline earth metal oxides:

  • Basic oxides, react with water to form hydroxides
  • Basicity decreases down the group, beryllium oxide least basic

• Alkaline earth metal carbonates:

  • Less soluble in water compared to alkali metal carbonates
  • Thermal stability increases down the group, beryllium carbonate decomposes easily

• Applications:

  • Calcium: cement, plaster, fertilizers, medicine (bones and teeth)
  • Magnesium: alloys, lightweight construction materials, photography

Relevant NCERT references (Class 12):

• Chapter 4, The d- and f-Block Elements
• Section 4.3, The First Transition Series (3d-Series)
• Section 4.3.1, General Characteristics of the Transition Elements

Group 13 Elements (Boron Family)

Key points:

• General characteristics and trends:

  • Abundance: boron and aluminum most abundant, thallium least
  • Allotropy in boron (amorphous, crystalline)
  • Chemical properties dominated by the presence of empty p-orbital except boron

• Bonding in boranes:

  • Electron-deficient molecules, Lewis acids
  • Various bonding modes (2c-3e bonds)

• Properties and reactions of boron halides:

  • Covalent compounds, colorless and non-flammable
  • Lewis acids, react with water to form oxyacids

• Boric acid and its derivatives:

  • Weak acid, antiseptic and flame retardant properties
  • Borax: sodium tetraborate, water softener, flux in soldering

• Applications:

  • Boron: heat-resistant materials (borosilicate glass), semiconductors
  • Aluminum: lightweight, construction, transportation, packaging

Relevant NCERT references:

• Boron:

• Class 11: Chapter 11, Some p-Block Elements

  • Section 11.1, General Introduction
  • Section 11.2, Electronic Configuration
  • Section 11.8, Oxoacids of Boron

• Aluminum:

• Class 11: Chapter 12, Organic Chemistry – Some Basic Principles and Techniques

  • Section 12.1, General Introduction
  • Section 12.11, Aluminium Alkyls and Aryls

Group 14 Elements (Carbon Family)

Key points:

• General characteristics and trends:

  • Abundance: carbon most abundant, lead least
  • Catena and polycatena formations
  • Allotropes of carbon (graphite, diamond, fullerenes)
  • Abundance of carbon compounds due to tetravalency and the ability to form covalent bonds

• Allotropes of carbon:

  • Graphite: layered structure, soft and conducts electricity
  • Diamond: tightly bonded, hardest natural substance
  • Fullerenes: soccer ball-like molecules (e.g. buckminsterfullerene)

• Covalent bonding in carbon compounds:

  • Tetravalency of carbon, ability to form single, double, and triple bonds

• Hydrocarbons:

  • Saturated (alkanes) and unsaturated (alkenes, alkynes) hydrocarbons
  • Functional groups: alcohols, ethers, aldehydes, ketones, carboxylic acids, esters

• Organic reactions:

  • Substitution, addition, elimination, and condensation reactions

• Applications:

  • Fuels, plastics, pharmaceuticals, solvents, dyes, synthetic fibers

Relevant NCERT references:

• Carbon:

• Class 11: Chapter 12, Organic Chemistry – Some Basic Principles and Techniques

  • Section 12.1, General Introduction
  • Section 12.1.2, Carbon and its Compounds

• Hydrocarbons and functional groups:

• Class 12: Chapter 12 and Chapter 13

Group 15 Elements (Nitrogen Family)

Key points:

• General characteristics and trends:

  • Abundance: nitrogen and phosphorus most abundant, bismuth least
  • Allotropes of nitrogen (N2, N4) and phosphorus (white, red, black)

• Nitrogen fixation:

  • Conversion of atmospheric nitrogen into compounds useful to plants

• Ammonia and its properties:

  • Basic compound, colorless and pungent smelling gas
  • Production via Haber process, essential for fertilizer production

• Nitric acid and its derivatives:

  • Strong acid, corrosive and oxidizing properties
  • Used in fertilizers, explosives, and polymers

• Oxides of nitrogen and their environmental impact:

  • Various oxides, e.g. NO, NO2, N2O
  • Pollutants responsible for acid rain and ozone depletion

• Phosphorus and its allotropes:

  • Allotropes: white, red, black
  • White phosphorus: highly reactive, toxic, and luminescent
  • Red phosphorus: less reactive, used in safety matches

• Phosphoric acid and its derivatives:

  • Strong acid, used in fertilizers, detergents, and food additives

Relevant NCERT references:

• Nitrogen:

• Class 11: Chapter 9, Hydrogen

  • Section 9.5, Nitrogen Fixation

• Class 12: Chapter 6, General Organic Chemistry

  • Section 6.1, Preparation and Properties of Alkanes

• Phosphorus:

• Class 11: Chapter 11, Some p-Block Elements

  • Section 11.3, Electronic Configuration
  • Section 11.16, Preparation of Phosphine and Phosphonium Halides

Group 16 Elements (Oxygen Family)

Key points:

• General characteristics and trends:

  • Reactive non-metals, essential for life
  • Abundance: oxygen most abundant, polonium least

• Oxygen and its allotropes:

  • Two allotropes: oxygen (O2) and ozone (O3)
  • Ozone: protective layer against harmful UV radiations

• Ozone and its role in the atmosphere:

  • Stratospheric ozone: shields Earth from harmful UV radiations
  • Tropospheric ozone: air pollutant, harmful to respiratory system

• Water and its properties:

  • Unique properties, high surface tension and specific heat capacity
  • Polarity, hydrogen bonding, and its effects on various properties

• Hydrogen peroxide and its oxidizing properties:

  • Strong oxidizing agent, used in various applications

• Sulfur and its allotropes:

  • Allotropes: rhombic, monoclinic, and amorphous sulfur
  • Crown (S8) and cyclic allotropes

• Sulfuric acid and its derivatives:

  • Highly corrosive, strong acid
  • Widely used in various industries (e.g. fertilizers, batteries, explosives)

Relevant NCERT references:

• Oxygen:

• Class 11: Chapter 9, Hydrogen

  • Section 9.1, Electronic Structure of Elements

• Water:

• Class 11: Chapter 10, The s-Block Elements

  • Section 10.11, Biological Significance of Alkali and Alkaline Earth Metals

• Sulfur and its allotropes:

• Class 11: Chapter 12, Organic Chemistry – Some Basic Principles and Techniques

  • Section 12.1, General Introduction
  • Section 12.1.2, Carbon and its Compounds

Group 17 Elements (Halogens)

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