Detailed Notes for Chemistry of P-Block Elements - Group 13

1. General Properties of Group 13 Elements

Key Points:

• Electronic configuration: All group 13 elements have an outer electronic configuration of ns2 np1 (where n is the principal quantum number).
• Atomic radii trends: Atomic radii generally decrease down the group due to an increase in effective nuclear charge.
• Oxidation states: The most common oxidation state for group 13 elements is +3, but some can also exhibit +1 and +5 oxidation states.
• Stability of oxidation states: The +3 oxidation state is generally the most stable, followed by +1 and then +5.
• Physical properties: Group 13 elements are typically soft and have relatively low melting and boiling points.
• Allotropy: Some group 13 elements, like boron, exhibit allotropy (existence of different structural forms).

NCERT References:

• NCERT Class 11: Chapter 14 - p-Block Elements, Section 14.1 - Properties of Group 13 Elements

2. Boranes

Key Points:

• Structure: Boranes are molecules that contain boron atoms bonded to hydrogen atoms. The most common borane is diborane (B2H6), which has a unique “banana-shaped” structure due to electron deficiency.
• Bonding: Boranes have electron-deficient bonds, involving three-center two-electron bonds.
• Classification: Boranes can be classified into closo-, nido-, and arachno-boranes based on their structural characteristics.
• Properties and reactions: Boranes are colorless gases with a characteristic odor. They are highly reactive and can undergo a variety of reactions, such as hydroboration, dehydroboration, and oxidation.

NCERT References:

• NCERT Class 12: Chapter 9 - Coordination Compounds, Section 9.6 - Boranes

3. Aluminium

Key Points:

• Properties: Aluminium is a silvery-white metal with a high melting point and low density. It is resistant to corrosion, ductile, and malleable.
• Extraction: Bauxite is the primary ore of aluminium, and the Bayer’s process is used for its extraction.
• Production of alumina: Alumina is obtained by heating bauxite and treating it with sodium hydroxide solution.
• Production of aluminium metal: Aluminium is produced through the electrolysis of molten alumina in a Hall-Héroult cell.

NCERT References:

• NCERT Class 11: Chapter 14 - p-Block Elements, Section 14.7 - Aluminium
• NCERT Class 12: Chapter 2 - Solutions, Section 2.14 - Colloids (Aluminium Hydroxide)

4. Aluminium Compounds

Key Points:

• Aluminium halides: Aluminium halides are covalent compounds with general formula AlX3. They are Lewis acids and can undergo hydrolysis reactions.
• Aluminium oxides: Aluminium forms various oxides, including alumina (Al2O3), which is a white, solid compound with high melting and boiling points. It is amphoteric and forms aluminates with bases.
• Aluminium hydroxides: Aluminium hydroxide is a white, gelatinous solid that is insoluble in water. It is amphoteric and reacts with both acids and bases.

NCERT References:

• NCERT Class 11: Chapter 14 - p-Block Elements, Section 14.8 - Compounds of Aluminium

5. Gallium and Indium

Key Points:

• Properties: Gallium and indium are soft, silvery-white metals with low melting points. They are ductile and exhibit malleability.
• Extraction: Gallium and indium are obtained as by-products of zinc and lead refining processes, respectively.
• Compounds: Gallium and indium form compounds analogous to those of aluminium, such as gallium halides, oxides, and hydroxides.
• Applications: Gallium and indium have applications in electronics (semiconductors), alloys, and specialized materials (e.g., gallium arsenide in solar cells and LEDs).

NCERT References:

• NCERT Class 11: Chapter 14 - p-Block Elements, Section 14.9 - Gallium and Indium

6. Thallium

Key Points:

• Properties: Thallium is a soft, bluish-white metal that tarnishes in air. It is toxic and has low melting and boiling points.
• Extraction: Thallium is obtained as a byproduct of lead and zinc refining processes.
• Compounds: Thallium forms compounds analogous to those of the other group 13 elements. However, thallium(III) compounds are more stable than those of other group 13 elements.
• Toxicity: Thallium and its compounds are highly toxic, and ingestion can lead to severe health issues.

NCERT References:

• NCERT Class 11: Chapter 14 - p-Block Elements, Section 14.10 - Thallium

7. Interhalogen Compounds

Key Points:

• Formation: Interhalogen compounds are formed by the direct combination of different halogen elements.
• Structure: Interhalogen compounds have various structures, depending on the combination of halogens. Some common structures include linear, T-shaped, and square planar.
• Properties: Interhalogen compounds are typically volatile, colored compounds. They are reactive and can undergo a variety of reactions, including hydrolysis, addition reactions, and halogen exchange reactions.
• Oxidizing and reducing abilities: Depending on the composition, interhalogen compounds can act as either oxidizing or reducing agents.

NCERT References:

• NCERT Class 11: Chapter 15 - The d-Block Elements, Section 15.17 - Interhalogen Compounds