Group 13: Boron Family (The Icosagens)

Group 13 of the periodic table is known as the Boron Family or Icosagens. It includes boron (B), aluminum (Al), gallium (Ga), indium (In), and thallium (Tl). These elements have the general electronic configuration ns² np¹. Periodic trends in this group show increasing metallic nature, while the heavier members like thallium exhibit the +1 oxidation state due to the inert pair effect. For extended reading, see Britannica’s guide on Boron Group elements.

General Characteristics

• Electronic Configuration: ns² np¹ outer configuration.
• Metallic Character: Boron is a metalloid; others are metals with increasing metallic nature down the group.
• Oxidation States: Predominantly +3; Tl shows +1 due to inert pair effect.
• Atomic and Ionic Size: Increase down the group.
• Electronegativity: Highest in boron, decreases down the group.

Physical Properties

• Boron is a hard, black metalloid with a high melting point.
• Aluminum is lightweight, silvery-white, malleable, and a good conductor.
• Gallium, indium, and thallium are soft metals; gallium melts near room temperature.
• Density and melting points increase down the group (with anomalies).

Chemical Properties

• Boron forms covalent compounds; heavier elements form more ionic compounds.
• Oxides: B₂O₃ (acidic), Al₂O₃ (amphoteric), Tl₂O (basic).
• Boron compounds act as Lewis acids due to vacant p-orbitals.
• Thallium shows +1 oxidation state (inert pair effect).
• Boron hydrides (boranes) are electron-deficient and show cluster bonding.

Important Compounds and Uses

• Boron Compounds: Borax (glass & detergents), boric acid (antiseptic).
• Aluminum: Packaging, construction, aircraft, and electrical industries.
• Gallium: Semiconductors, LEDs, solar panels.
• Thallium: Electronics (toxic, limited use).

Trends in Group 13

• Inert Pair Effect: Increases down the group; Tl shows stable +1 state.
• Reactivity: Increases down the group as metallic nature increases.
• Acidity of Oxides: Boron oxide (acidic), Al₂O₃ (amphoteric), Tl₂O (basic).

MCQs: Test Your Knowledge

1. Which oxidation state is common in Group 13 elements?
2. Which element in Group 13 prominently shows inert pair effect?
3. Which group 13 metal melts near room temperature?
4. Boron compounds often behave as:
   1. Lewis acids
   2. Lewis bases
   3. Oxidizing agents
   4. Strong bases
5. Which oxide is amphoteric in Group 13?

MCQ Answers

• +3 oxidation state
• Thallium (Tl)
• Gallium (Ga)
• Lewis acids
• Aluminum oxide (Al₂O₃)

FAQs on Group 13 Elements

Q1: Why is boron different from other group 13 elements?
Boron is a metalloid with covalent bonding, unlike metallic members such as Al, Ga, In, Tl.

Q2: What is the inert pair effect in group 13?
It is the reluctance of ns² electrons to participate in bonding, leading to +1 oxidation state (especially in Tl).

Q3: Why is aluminum oxide amphoteric?
Because it reacts with both acids and bases, forming salts in each case.

Q4: What are boron hydrides used for?
They are studied in cluster chemistry and used as rocket fuels and reducing agents.

Next: Group 14: Carbon Family