What NEET Asks
- Direct questions on physical properties (e.g., hardness, conductivity) are common.
- Reaction mechanisms and products with various reagents (O2, acids, alkalis, halogens) are frequently tested.
- Comparative properties of Boron within Group 13 are important for understanding its anomalous behavior.
Key Points
- Boron is a non-metallic element (metalloid) existing in several allotropic forms; crystalline boron is the most common.
- Crystalline boron is extremely hard, dark, and possesses a very high melting point (~2300 °C).
- It is a poor electrical conductor at room temperature, acting as a semiconductor at higher temperatures.
- Due to its small size and high ionization energy, boron forms predominantly covalent compounds.
- It is largely inert to acids and alkalis at room temperature but reacts vigorously upon heating.
- Boron is electron deficient (only 3 valence electrons), which makes its compounds, like BX3, strong Lewis acids.
Must-Know Formula / Reaction
- 4B(s) + 3O2(g) → 2B2O3(s): Boron reacts with oxygen at high temperatures to form boric anhydride.
B: Boron elementO2: Oxygen gasB2O3: Boron trioxide (boric anhydride)
Common Mistakes
- Students often confuse boron's inertness at room temperature with its high-temperature reactivity.
- Don't assume boron is a good conductor like other metals in its group; it's a semiconductor.
- Misinterpreting boron's covalent nature and electron deficiency, leading to incorrect predictions about its bonding and Lewis acid character.
Rapid Revision
Boron is a hard, high-melting point semiconductor, non-metallic. It's inert at room temp but reacts at high temp with O2 (forming B2O3), halogens (forming BX3), and strong oxidizing acids (forming H3BO3). Boron forms covalent, electron-deficient compounds.