- 🇬🇧 Boron
- 🇺🇦 Бор
- 🇨🇳 硼
- 🇳🇱 Boor
- 🇫🇷 Bore
- 🇩🇪 Bor
- 🇮🇱 בור
- 🇮🇹 Boro
- 🇯🇵 ホウ素
- 🇵🇹 Boro
- 🇪🇸 Boro
- 🇸🇪 Bor
- 🇷🇺 Бор
- Name: boron
- Symbol: B
- Atomic number: 5
- Relative atomic mass (Ar): 10.81 range: [10.806, 10.821] m [see notes g m r]
- Standard state: solid at 298 K
- Appearance: black
- Classification: Semi-metallic
- Group in periodic table: 13
- Group name: (none)
- Period in periodic table: 2
- Block in periodic table: p
- Shell structure: 2.3
- CAS Registry: 7440-42-8
Boron atoms have 5 electrons and the shell structure is 2.3. The ground state electronic configuration of neutral boron is [He].2s2.2p1 and the term symbol of boron is 2P1/2.
Boron: description
Boron is a Group 13 element that has properties which are borderline between metals and non-metals (semimetallic). It is a semiconductor rather than a metallic conductor. Chemically it is closer to silicon than to aluminium, gallium, indium, and thallium.
Crystalline boron is inert chemically and is resistant to attack by boiling HF or HCl. When finely divided it is attacked slowly by hot concentrated nitric acid.
boron
Image adapted with permission from Prof James Marshall's (U. North Texas, USA) Walking Tour of the elements CD.
Boron: physical properties
- Density of the chemical elements on a miniature periodic table spark table Density of solid: 2460 kg m-3
- Molar volume of the chemical elements on a miniature periodic table spark table Molar volume: 4.39 cm3
- Thermal conductivity of the chemical elements on a miniature periodic table spark table Thermal conductivity: 27 W m‑1 K‑1
Boron: heat properties
- Melting point on a miniature periodic table spark table Melting point: 2349 [2076 °C (3769 °F)] K
- Boiling point on a miniature periodic table spark table Boiling point: 4200 [3927 °C (7101 °F)] K
- Enthalpy of fusion on a miniature periodic table spark table Enthalpy of fusion: 20.5 kJ mol-1
Boron: atom sizes
- Atomic radius (empirical) of the chemical elements on a miniature periodic table spark table Atomic radius (empirical): 85 pm
- Covalent (single bond) radius on a periodic table spark table Molecular single bond covalent radius: 85 (coordination number 3) ppm
- van der Waals radius on a periodic table spark table van der Waals radius: 191 ppm
Boron: electronegativities
- Pauling electronegativity of the chemical elements on a miniature periodic table spark table Pauling electronegativity: 2.04 (Pauling units)
- Allred-Rochow electronegativity of the chemical elements on a miniature periodic table spark tableAllred Rochow electronegativity: 2.01 (Pauling units)
- Mulliken-Jaffe electronegativity of the chemical elements on a miniature periodic table spark tableMulliken-Jaffe electronegativity: 2.04 (sp2 orbital)
Boron: orbital properties
- First ionization energy the chemical elements on a miniature periodic table spark table First ionisation energy: 800.64 kJ mol‑1
- Second ionization energy the chemical elements on a miniature periodic table spark table Second ionisation energy: 2427.07 kJ mol‑1
- Third ionization energy the chemical elements on a miniature periodic table spark table Third ionisation energy: 3659.74 kJ mol‑1
Boron: abundances
- Chemical elements abundance by weight in the universe on a miniature periodic table spark tableUniverse: 1 ppb by weight
- Chemical elements abundance by weight in the earth's crust on a miniature periodic table spark tableCrustal rocks: 8700 ppb by weight
- Chemical elements abundance by weight in humans on a miniature periodic table spark tableHuman: 700 ppb by weight
Boron: crystal structure
Boron: biological data
- Human abundance by weight of the chemical elements on a miniature periodic table spark table Human abundance by weight: 700 ppb by weight
Boron is probably not required in the diet of humans but it might be a necessary "ultratrace" element. Boron is required by green algae and higher plants.
Boron: uses
Boron: reactions
Reactions of boron as the element with air, water, halogens, acids, and bases where known.
Boron: binary compounds
Binary compounds with halogens (known as halides), oxygen (known as oxides), hydrogen (known as hydrides), and other compounds of boron where known.
Boron: compound properties
Bond strengths; lattice energies of boron halides, hydrides, oxides (where known); and reduction potentials where known.
Boron: history
Boron was discovered by Sir Humphrey Davy, Joseph-Louis Gay-Lussac, L.J. Thénard in 1808 at England and France. Origin of name: from the Arabic word "buraq" and the Persian word "burah" .Boron: isotopes
Both isotopes of Boron, B-10 and B-11, are used extensively in the nuclear industry. B-10 is used in the form of boric acid as a chemical shim in pressurized water reactors while in the form of sodium pentaborate it is used for standby liquid control systems in boiling water reactors. B-11 can be used as a neutron reflector. Outside the nuclear industry both isotopes are used as food label to study boron metabolism. B-10 is also used in so-called boron neutron capture therapy (BNCT). Both B-10 and B-11 can be used for the production of two radioisotopes: C-11 and N-13.
Boron: isolation
Isolation: it is not normally necessary to make boron in the laboratory and it would normally be purchased as it is available commercially. The most common sources of boron are tourmaline, borax [Na2B4O5(OH)4.8H2O], and kernite [Na2B4O5(OH)4.2H2O]. It is difficult to obtain pure. It can be made through the magnesium reduction of the oxide, B2O3. The oxide is made by melting boric acid, B(OH)3, which in turn is obtained from borax.
B2O3 + 3Mg → 2B + 3MgO
Samm amounts of high purity boron are available through the thermal decomposition of compounds such as BBr3 with hydrogen gas using a heated tantalum wire. Results are better with hot wires at tmeperatures over 1000°C.