# بور

Boron,  5B|  |
| General properties |
| Allotropes | α-, β-rhombohedral, β-tetragonal (and more) |
| Appearance | black-brown |
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| Boron in the periodic table |
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 | – ↑ B ↓ Al |
| beryllium ← boron → carbon | ‍ |

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 |
| Atomic number (*Z*) | 5 |
| Group, period | group 13 (boron group), period 2  |
| Block | p-block  |
| Electron configuration | {{{electron configuration}}}  |
| Electrons per shell | 2, 3 |
| Physical properties |
| Melting point | 2349 K ​(2076 °C, ​3769 °F)  |
| Boiling point | 4200 K ​(3927 °C, ​7101 °F)  |
| Density when liquid, at m.p. | 2.08 g/cm3  |
| Heat of fusion | 50.2 kJ/mol  |
| Heat of vaporization | 508 kJ/mol  |
| Molar heat capacity | 11.087 J/(mol·K)  |
| **Vapor pressure** |-
! style="text-align:right;" | 10B
| style="text-align:right" | 20%
| colspan="3" style="text-align:left;" | is stable
|-
! style="text-align:right;" | 11B
| style="text-align:right" | 80%
| colspan="3" style="text-align:left;" | is stable

| *P* (Pa) | 1 | 10 | 100 | 1 k | 10 k | 100 k |
| --- | --- | --- | --- | --- | --- | --- |
| at *T* (K) | 2348 | 2562 | 2822 | 3141 | 3545 | 4072 |

 |
| Atomic properties |
| Electronegativity | Pauling scale: 2.04  |
| Ionization energies | 1st: 800.6 kJ/mol  2nd: 2427.1 kJ/mol  3rd: 3659.7 kJ/mol  (more)  |
| Atomic radius | empirical: 90 pm  |
| Covalent radius | 84±3 pm  |
| Van der Waals radius | 192 pm  |
| Miscellanea |
| Crystal structure |  ​rhombohedral |
| Speed of sound  thin rod | 16,200 m/s (at 20 °C)  |
| Thermal expansion | β form: 5–7 µm/(m·K) (at 25 °C)  |
| Thermal conductivity | 27.4 W/(m·K)  |
| Electrical resistivity | ~106 Ω·m (at 20 °C)  |
| Magnetic ordering | diamagnetic  |
| Magnetic susceptibility (*χ*mol) | −6.7·10−6 cm3/mol |
| Mohs hardness | ~9.5  |
| CAS Number | 7440-42-8  |
| تاریخی |
| Discovery | Joseph Louis Gay-Lussac and
Louis Jacques Thénard (30 June 1808) |
| First isolation | Humphry Davy (9 July 1808) |
| Main isotopes of boron |
|

| Iso­tope | Abun­dance | Half-life | Decay mode | Pro­duct

 |
| --- | --- | --- | --- | --- |

 |
| 10B content is 19.1–20.3% in natural samples, with the remainder being 11B. |
|

بور
**بور**

## قایناقلار

شابلون:قتیناق

### اتک‌یازی