Boron: Physical and Chemical Properties and Compounds
Details physical and chemical properties of boron and important compounds like borax, boric acids, and boron hydrides.
What is Boron: Physical and Chemical Properties and Compounds?
An element having properties intermediate between those of metals and non-metals.
Key formula / rule: Borax
Key points
- Describe the physical and chemical properties of boron.
- Explain the allotropy of boron.
- Identify and describe the preparation and properties of borax and boric acid.
- Understand the structure and bonding in boron hydrides, especially diborane.
Common exam trap
Confusing boric acid as a Brønsted acid (it's a Lewis acid).
Definitions
- Term
Metalloid
- Meaning
An element having properties intermediate between those of metals and non-metals.
- Term
Allotropy
- Meaning
The property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes.
- Term
Lewis Acid
- Meaning
A chemical species that can accept an electron pair from a Lewis base to form a covalent bond.
- Term
Electron-deficient compound
- Meaning
A compound where the atoms do not have a complete octet of electrons, often leading to unique bonding or reactivity.
- Term
2-electron, 3-center bond
- Meaning
A type of delocalized covalent bond involving three atoms and only two electrons, commonly found in electron-deficient molecules like diborane.
Learning objectives
Describe the physical and chemical properties of boron.
Explain the allotropy of boron.
Identify and describe the preparation and properties of borax and boric acid.
Understand the structure and bonding in boron hydrides, especially diborane.
Recognize boron's electron-deficient nature in its compounds.
Formulae
- Name
Borax
- Note
Sodium tetraborate decahydrate
- Expression
Na₂B₄O₇·10H₂O
- Name
Boric Acid
- Note
Orthoboric acid
- Expression
H₃BO₃
- Name
Diborane
- Note
Simplest borane, dimer of BH₃
- Expression
B₂H₆
- Name
Borax Heating
- Note
Anhydrous borax formation
- Expression
Na₂B₄O₇·10H₂O → (Heat) → Na₂B₄O₇ + 10H₂O
- Name
Borax Bead Test
- Note
Formation of sodium metaborate and boron trioxide
- Expression
Na₂B₄O₇ (anhydrous) → (Heat) → 2NaBO₂ + B₂O₃
- Name
Boric Acid as Lewis Acid
- Note
Accepts hydroxide ion
- Expression
H₃BO₃ + OH⁻ → [B(OH)₄]⁻
Prerequisites
Basic understanding of atomic structure and electronic configuration.
Knowledge of periodic trends (ionization enthalpy, atomic radius).
Understanding of chemical bonding (covalent, ionic, Lewis acid-base).
Familiarity with chemical nomenclature and formulas.
Common mistakes
Confusing boric acid as a Brønsted acid (it's a Lewis acid).
Incorrectly assuming boron forms ionic compounds readily.
Not recognizing the unique bonding in diborane.
Forgetting the formula and structure of borax.
Keywords
Boron
Group 13
Metalloid
Allotropy
Borax
Boric Acid
Boranes
Diborane
Lewis Acid
Electron deficient
2-electron 3-center bond
Practice preview
Boric acid, H₃BO₃, is a weak acid because:…
medium
The structure of diborane (B₂H₆) involves:…
hard
Which of the following statements about Boron is INCORRECT?…
easy