Main Group Elements: Properties and Applications

Main Group Elements: Characteristics and Applications

Group 3 Elements (Boron to Thallium)

The elements in Group 3 (Boron, Aluminum, Gallium, Indium, Thallium) share the electron configuration ns²p¹.

Properties of Boron and Aluminum

• Boron (B): A hard, brittle solid with poor electrical conductivity. It primarily forms covalent bonds, such as B-B.
• Aluminum (Al): A shiny, malleable, and ductile metal with good electrical conductivity. Its common oxidation number is +3.

Chemical Reactions and Characteristics

• Boron reacts with Chlorine at high temperatures to form boron trichloride.
• Aluminum burns vigorously when heated in oxygen:

  2Al + 3O2 → 2Al2O3

• Aluminum forms a self-protective layer of aluminum oxide (Al₂O₃) on its surface, which prevents further reactions with oxygen.

Group 4 Elements (Carbon to Lead)

Group 4 elements (Carbon, Silicon, Germanium, Tin, Lead) have an ns²p² electron configuration.

Bonding and Allotropes

• Carbon (C), Silicon (Si), and Germanium (Ge) primarily form covalent bonds by sharing electrons.
• Tin (Sn) and Lead (Pb) tend to react by losing electrons.
• Carbon Allotropes:
  • Diamond: A giant covalent structure characterized by strong single covalent bonds, making it extremely hard.
  • Graphite: A layered giant covalent structure with one free electron per carbon atom, making it electrically conductive.

Health and Industrial Applications

• Lead (Pb): A heavy metal with a high relative atomic mass. It is a cumulative poison that affects the central nervous system. Cumulative poisons are poorly excreted by the human body.
• Uses of Silicon (Si): Silicon occurs naturally in sand as silicon dioxide (SiO₂). It is crucial in the manufacturing of:
  • Alloys
  • Glass
  • Cement
  • Computer chips

Group 5 Elements (Nitrogen and Phosphorus)

Elements in Group 5 (Nitrogen and Phosphorus) have an ns²p³ electron configuration.

Properties and Reactivity

• Nitrogen (N): A gas at room temperature. The N≡N triple bond in N₂ makes it highly stable.
  • Nitrogen monoxide (NO) and dinitrogen monoxide (N₂O) are colorless gases.
  • Nitrogen dioxide (NO₂) is a brown gas.
• Reaction Example: Copper reacting with nitric acid:

  3Cu + 8HNO3 → 3Cu(NO3)2 + 2NO + 4H2O

• Phosphorus (P): Very reactive and exists in several allotropic forms (e.g., P₄). White phosphorus (P₄) must be stored underwater because it ignites spontaneously in air.
• Both Phosphorus and Nitrogen exhibit a wide range of oxidation numbers, varying from -3 to +5.

Biochemical Importance and Uses

• Nitrogen and Phosphorus play vital roles in biochemistry, being essential components of:
  • DNA
  • RNA
  • ATP (Adenosine Triphosphate)
• Key Uses:
  • Ammonia: Primarily used as a fertilizer.
  • Red Phosphorus: Used in matches.
  • Antimony: Often used in alloys.

Group 6 Elements (Oxygen)

Group 6 elements, including Oxygen, have an ns²p⁴ electron configuration.

Oxygen's Role and Properties

• Oxygen (O) readily gains two electrons to form the oxide ion (O^2-), achieving a stable electron configuration similar to Neon.
• It is the second most reactive nonmetal, reacting with both metals and nonmetals.
• Oxygen constitutes approximately 21% of the Earth's atmosphere and 51% of the Earth's crust by volume.
• Oxygen gas is commercially obtained by the fractional distillation of liquefied air.

Allotropes and Reactions

• Oxygen has two main allotropes:
  • Oxygen (O₂): The common diatomic gas.
  • Ozone (O₃): A highly unstable and reactive gas. In the lower atmosphere, it is considered a pollutant, but in the upper atmosphere (stratosphere), the ozone layer protects Earth from harmful UV radiation.
• Oxygen is a powerful oxidizing agent. Examples of reactions:

  4Na + O2 → 2Na2O

  2Ca + O2 → 2CaO

  C + O2 → CO2

  S + O2 → SO2

Group 7 Elements (Halogens: Fluorine to Iodine)

The Halogens (Fluorine, Chlorine, Bromine, Iodine) are highly reactive nonmetals.

General Characteristics

• They exist as diatomic molecules (e.g., F₂, Cl₂).
• Halogens produce colored vapors and are generally poisonous.
• They have relatively low boiling points.
• In solid form, they are brittle and crumbly.
• Halogens are non-conductive.

Reactivity

• When reacting with metals, halogens gain an electron from the metal to form ionic compounds.
• When reacting with nonmetals, electrons are shared to form covalent bonds.

Group 0 Elements (Noble Gases: Helium to Xenon)

The Noble Gases (Helium, Neon, Argon, Krypton, Xenon) are nonmetals known for their inertness.

Properties and Applications

• They are colorless, monatomic gases.
• Noble gases are largely unreactive due to having a full valence electron shell, which makes them chemically stable.
• Key Uses:
  • Helium (He): Used in balloons and airships due to its low density and non-flammability.
  • Neon (Ne): Used in fluorescent signs, producing a distinctive orange-red glow.
  • Argon (Ar): Commonly used in lightbulbs to prevent the filament from oxidizing.
  • Krypton (Kr): Utilized in certain types of lasers.