The Chem Sketchbook

The Chem Sketchbook Chemistry notes simplified through infographics. 📝 Custom-made study guides for the modern student.

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Trihalides — The Fascinating Chemistry of BF₃!Boron trihalides are an important class of Group 13 compounds, with BF₃ ...
20/08/2026



Trihalides — The Fascinating Chemistry of BF₃!
Boron trihalides are an important class of Group 13 compounds, with BF₃ being the most significant member. Its chemistry beautifully demonstrates how electron deficiency, π bonding and Lewis acidity are interconnected.

🔹 BF₃ is planar (sp² hybridized) with a bond angle of 120°.
🔹 Boron has only six electrons around it, making BF₃ electron deficient.
🔹 Delocalized pπ–pπ bonding gives all three B–F bonds identical character.
🔹 The empty 2p orbital allows BF₃ to accept electron pairs, making it a strong Lewis acid.
🔹 BF₃ forms tetrahedral complexes with donors such as NH₃, Et₂O and F⁻.
🔹 It plays an important role in industrial chemistry and organic reactions, including Friedel–Crafts reactions and acid-catalyzed processes.

Tetrahydridoborates: When [BH₄]⁻ Acts as a Ligand!Not all borohydrides are ionic! As we move to Be, Al and transition-...
20/08/2026



Tetrahydridoborates: When [BH₄]⁻ Acts as a Ligand!

Not all borohydrides are ionic! As we move to Be, Al and transition-metal borohydrides, covalent character increases and the [BH₄]⁻ ion can act as a bridging ligand.

🔹 Three-centre, two-electron (3c–2e) bonds are formed when H atoms bridge the metal and boron.
🔹 Compounds such as Be(BH₄)₂ and Al(BH₄)₃ show this unusual bonding.
🔹 Li[AlH₄] (LiAlH₄) is a powerful reducing agent widely used in organic chemistry, but it cannot be used in aqueous solutions.
🔹 Gallium forms Li[GaH₄], while indium forms polymeric (InH₃)ₙ.

📌 Exam Tip: Remember the unusual 3c–2e hydrogen-bridged bonding in covalent borohydrides!

Save this infographic for your inorganic chemistry revision. ⚗️

Tetrahydridoborates (Borohydrides) — Chemistry at a Glance!Tetrahydridoborates contain the tetrahedral [BH₄]⁻ ion, wit...
20/08/2026



Tetrahydridoborates (Borohydrides) — Chemistry at a Glance!

Tetrahydridoborates contain the tetrahedral [BH₄]⁻ ion, with Na[BH₄] (sodium borohydride) being the most important member.

✨ Key points to remember:
• Na[BH₄] has an ionic, NaCl-type structure.
• It is prepared from trimethylborate under suitable conditions.
• Alkali metal tetrahydridoborates show different reactivities toward water.
• Na[BH₄] is a valuable reducing agent in organic and inorganic chemistry.
• It selectively reduces aldehydes → primary alcohols and ketones → secondary alcohols.
• C=C, –COOH and –NO₂ groups are generally not attacked under typical conditions.

📚 A must-know reagent for inorganic & organic chemistry exams!

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Amphoteric Behaviour of Al(OH)₃ & AluminatesAluminium hydroxide is a classic example of an amphoteric hydroxide—it can...
19/08/2026



Amphoteric Behaviour of Al(OH)₃ & Aluminates
Aluminium hydroxide is a classic example of an amphoteric hydroxide—it can react with both acids and strong bases!

🔹 With acids → forms hydrated Al³⁺ salts
🔹 With excess NaOH → forms sodium aluminate, commonly represented as NaAl(OH)₄ or NaAlO₂·2H₂O
🔹 The structure of aluminate species depends strongly on pH and concentration—from polymeric species to tetrahedral [Al(OH)₄]⁻ and dimeric species.

Group 13 trend:
Ga₂O₃ and Ga(OH)₃ retain amphoteric character, whereas In₂O₃ and Tl₂O₃ are predominantly basic. The lower oxidation state becomes increasingly basic down the group.

Exam tip: Amphoterism generally decreases down Group 13.

Save this infographic for quick Inorganic Chemistry revision!

Exploring Aluminium Oxide (Alumina), Al₂O₃!Alumina exists mainly in two crystalline forms: α-Al₂O₃ (corundum) and γ-Al...
19/08/2026



Exploring Aluminium Oxide (Alumina), Al₂O₃!

Alumina exists mainly in two crystalline forms: α-Al₂O₃ (corundum) and γ-Al₂O₃, each with distinct properties and applications.

Key takeaways: • α-Al₂O₃ is exceptionally hard, chemically resistant and useful as a refractory and polishing material.

• γ-Al₂O₃ is acid-soluble, water-absorbing and widely used as a chromatography adsorbent.
• Gem-quality corundum gives us ruby and sapphire 💎
• Fibrous Al₂O₃ (Saffil) offers high strength, thermal stability and excellent insulating properties.
• Aluminium’s strong affinity for oxygen makes thermite reactions possible.

Remember: The very high stability of Al₂O₃ is reflected in its highly negative enthalpy of formation, making aluminium an excellent reducing agent for less stable metal oxides.

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BORIDES — The Hard & High-Temperature Compounds of Boron!Borides are fascinating binary compounds formed between boron...
18/08/2026



BORIDES — The Hard & High-Temperature Compounds of Boron!
Borides are fascinating binary compounds formed between boron and metals, with a remarkable diversity of compositions and structures.

🔹 Common stoichiometries include M₂B, MB, MB₂, MB₄ and MB₆.
🔹 Many borides are hard, chemically inert and have extremely high melting points.
🔹 Some, such as ZrB₂, HfB₂, NbB₂ and TaB₂, melt above 3000°C!
🔹 Their unusual structures can involve multi-centre bonding.

⭐ Boron carbide (B₄C) is particularly important—used as an abrasive, in brake linings and for high-strength fibres.

🚀 Borides also find applications in turbine components, rocket nozzles and high-temperature materials.

☢️ Boron steel is used in nuclear technology because ¹⁰B has a very high absorption cross-section for thermal neutrons.

Key takeaway: Borides combine exceptional hardness, thermal stability, chemical inertness and electrical properties, making them valuable advanced materials.

Save this infographic for your Inorganic Chemistry revision!

Qualitative Analysis of Boron Compounds — A Characteristic Green Flame Test! How can the presence of boron in a compou...
18/08/2026



Qualitative Analysis of Boron Compounds — A Characteristic Green Flame Test!

How can the presence of boron in a compound be detected?

🔹 BF₃ Test: Borates react with HF to form volatile BF₃. It can also be generated using concentrated H₂SO₄ and CaF₂. BF₃ introduced into a flame produces a characteristic green coloration.
🔹 Methyl Borate Test: Borates can be converted to boric acid and then reacted with methanol to form volatile methyl borate, B(OCH₃)₃. On burning, it also produces a green flame.

Remember:
Boron → volatile boron compound → green flame
A useful qualitative test to remember for Boron Chemistry & Inorganic Analysis!

Isopolyacids of B, Si & P — Understanding Polymeric Structures!Why do borates, silicates and phosphates form such fasc...
18/08/2026



Isopolyacids of B, Si & P — Understanding Polymeric Structures!

Why do borates, silicates and phosphates form such fascinating polymeric structures?

🔹 Isopolyacids contain only one type of acidic ion polymerized together.
🔹 Heteropolyacids contain two different types of ions, such as phosphate and molybdate.
🔹 Boron can form both triangular BO₃ and tetrahedral BO₄ units.
🔹 BO₃ units can link through shared oxygen atoms to form chains, rings and 2D sheets.
🔹 More complex borates may contain both BO₃ and BO₄ units.
🔹 Hydrated borates can accept protons and may polymerize through loss of H₂O.
🔹 In contrast, phosphates and silicates are based on tetrahedral PO₄ and SiO₄ units and generally form more stable polymeric frameworks.

Key takeaway: The geometry and polymerization of borate units are strongly influenced by hydration and protonation, making borate chemistry remarkably diverse!
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Sodium Peroxoborate (NaBO₃·4H₂O)A fascinating boron compound with an important role in detergent chemistry! 🔹 Produced...
18/08/2026



Sodium Peroxoborate (NaBO₃·4H₂O)

A fascinating boron compound with an important role in detergent chemistry!

🔹 Produced on a large industrial scale
🔹 Prepared by electrolysis of sodium borate or by oxidation using H₂O₂
🔹 Contains characteristic peroxide (O–O) linkages in the peroxoborate ion
🔹 Used as a brightener in washing powders
🔹 Compatible with enzymes used in some biological detergents
🔹 On heating in very hot water (>80°C), its peroxide linkages break down to produce H₂O₂

Chemistry takeaway: The O–O peroxide linkage is the key structural feature responsible for its oxidizing and bleaching properties.

Save this post for your Inorganic Chemistry revision! 📚⚗️

From Simple Triangles to Complex Networks — The Fascinating World of Borates! Borates exhibit remarkable structural di...
07/08/2026



From Simple Triangles to Complex Networks — The Fascinating World of Borates!

Borates exhibit remarkable structural diversity because BO₃ triangular units and BO₄ tetrahedral units can share corners to form chains, rings, sheets, and three-dimensional frameworks.
This unique ability gives rise to compounds with diverse physical and chemical properties, making boron chemistry one of the most interesting topics in inorganic chemistry.

📌 In this infographic, you'll learn:
🔹 Why boron forms trigonal planar BO₃ units
🔹 The layered hydrogen-bonded structure of orthoboric acid
🔹 How metaborates form chains and rings
🔹 The unique structures of borax and complex borates

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