Boron
An element of group 13 of the periodic table. There are two allotropes, amorphous boron is a brown power, but metallic boron is black. The metallic form is hard (9.3 on Mohs' scale) and a bad conductor in room temperatures. It is never found free in nature. Boron-10 is used in nuclear reactor control rods and shields. It was discovered in 1808 by Sir Humphry Davy and by J.L. Gay-Lussac and L.J. Thenard.
Gallery
Jurii, CC BY 3.0 <https://creativecommons.org/licenses/by/3.0>, via Wikimedia Commons, source: https://images-of-elements.com/boron.php
Physical Propertiesmass · density · phase · crystal
Atomic Mass
10.8100Da
Density
2.3400g/cm³
Phase (STP)
Solid
Melting Point
2350.2K
Boiling Point
4273.1K
Molar Heat
1.0260J/(mol·K)
Crystal Structure
TET
Lattice Constant
8.730Å
Atomic Radiiatomic · covalent · van der Waals
Atomic (Empirical)
85.00pm
Covalent
85.00pm
Van der Waals
192.00pm
Electronic Propertieselectronegativity · ionization · affinity
Electron Configuration
[He] 2s2 2p
Electron Shells
2, 3
Electronegativity
2.04Pauling
Electron Affinity
0.3kJ/mol
1st Ionization Energy
8.3kJ/mol
Oxidation States
-1, +1, +2, +3
Orbital DiagramAufbau · Hund's rule · Pauli exclusion
Full: 1s2 2s2 2p1Short: [He] 2s2 2p
Ionization Energies (5 known)
Emission Spectrumvisible range · characteristic spectral lines
Abundanceby mass
Log scale · ppm = parts per million by mass
Biological Role
Needed for plant cell wall structure. Likely essential in trace amounts for animals.
Discovery
Discovered By
Sir H. Davy, J.L. Gay-Lussac, L.J. Thénard
Named By
—
Year
1808
Nuclear Data
Known Isotopes
16
Stable Isotopes
3
Stable Mass Numbers
10, 11, 18
Natural isotopic abundance (IUPAC recommended values)
Isotopes of B16 known
| Nuclide | Z | N | Mass (AMU) | Half-life | Decay | Jπ | Abundance |
|---|---|---|---|---|---|---|---|
| 6B | 5 | 1 | 6.050800 | Unknown | 2p | 2- | — |
| 7B | 5 | 2 | 7.029712 | Unknown | p (1%) | 3/2- | — |
| 8B | 5 | 3 | 8.024607 | 772 ms | β⁺ (1%), β⁺α (1%) | 2+ | — |
| 10Bstable | 5 | 5 | 10.012937 | Stable | stable (1%) | 3+ | 1965.0000% |
| 11Bstable | 5 | 6 | 11.009305 | Stable | stable (1%) | 3/2- | 8035.0000% |
| 18Bstable | 5 | 13 | 18.055602 | Stable | n (1%) | 2- | — |
| 19B | 5 | 14 | 19.064166 | 2.92 ms | β⁻ (1%), β⁻n (0.71%), 2n (0.17%), 3n (0.091%) | 3/2- | — |
| 20B | 5 | 15 | 20.074506 | Unknown | n (1%), β⁻n, 2n | 1- | — |
| 21B | 5 | 16 | 21.084147 | Unknown | 2n (1%) | 3/2- | — |