# Rwbidiwm

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| --- |
| krypton ← **rwbidiwm** → strontium |
| K ↑ **Rb** ↓ Cs |

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**37Rb**
Y Tabl Cyfnodol |

 |

 |
| Ymddangosiad |
| llwydwyn  |
| Nodweddion cyffredinol |
| Enw, symbol, rhif | rwbidiwm, Rb, 37 |
| Ynganiad | /r**[invalid input: 'ʉ']**ˈbɪdiəm/ *roo-**BID**-ee-əm* |
| Teulu'r elfennau | alkali metal |
| Grŵp, cyfnod, bloc | 1, 5, s |
| Rhif atomig | 85.4678(3) |
| Patrwm yr Electronnau | [Kr] 5s1 |
| Electronnau / cragen | 2, 8, 18, 8, 1 (Image) |
| Nodweddion ffisegol |
| Stâd  | solid |
| Dwysedd (oddeutu tymheredd yr ystafell) | 1.532 g·cm−3 |
| Dwysedd hylif / Ymdoddbwynt | 1.46 g·cm−3 |
| Ymdoddbwynt | 312.46 K, 39.31 °C, 102.76 °F |
| Berwbwynt | 961 K, 688 °C, 1270 °F |
| Pwynt critigol | (extrapolated) 2093 K, 16 MPa |
| Enthalpi ymdoddiad
Gwres o ymdoddi | kJ·mol−1 |
| Enthalpi anweddiad | Cynhwysedd gwres | 31.060 J·mol−1·K−1 |
| Vapor pressure |
|

|  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- |
| P (Pa) | 1 | 10 | 100 | 1 k | 10 k | 100 k |
| at T (K) | 434 | 486 | 552 | 641 | 769 | 958 |

 |
| Nodweddion Atomig |
| cyflwr ocsidiad | 1 (strongly basic oxide) |
| Electronegativity | 0.82 (Graddfa Pauling) |
| Ionization energies | 1st: 403 kJ·mol−1 |
| 2: 2632.1 kJ·mol−1 |
| 3ydd: 3859.4 kJ·mol−1 |
| Radiws atomig | 248 pm |
| Radiws cofalent | 220±9 pm |
| Radiws Van der Waals | 303 pm |
| Amrywiol |
| Strwythyr y crisal | body-centered cubic |
| Magnetic ordering | paramagnetic |
| Gwrthedd trydanol | (20 °C) 128 nΩ·m |
| Dargludiad Thermal | 58.2 W·m−1·K−1 |
| Cyflymder sain | (20 °C) 1300 m·s−1 |
| Modwlws Young | 2.4 GPa |
| Modwlws Bulk | 2.5 GPa |
| Graddfa caledwch Mohs | 0.3 |
| Brinell hardness | 0.216 MPa |
| CAS registry number | 7440-17-7 |
| Most stable isotopes |
| Main article: Isotopes of rwbidiwm |
|

| iso | NA | half-life | DM | DE (MeV) | DP
Nodyn:Elementbox isotopes decay2
Nodyn:Elementbox isotopes decay4 |
| --- | --- | --- | --- | --- | --- |
| 85Rb | 72.168% | 85Rb is stable with 48 neutrons
Nodyn:Elementbox isotopes decay2 |
| 87Rb | 27.835% | 4.88 × 1010 y | β− | 0.283 | 87Sr |

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| * v
* t
* e
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Elfen gemegol yw **rwbidiwm** gyda'r rhif atomig 37 a'r symbol **Rb**. Mae'n rhan o'r metelau alcalïaidd yn y tabl cyfnodol. Metel feddal iawn yw rwbidiwm a gellir ei dorri gyda chyllell yn hawdd. Mae'r metel yn adweithiol iawn felly mae'r wyneb newydd yn sgleiniog, ond mae'n troi'n bŵl yn gyflym wrth i haen o rwbidiwm ocsid ffurfio dros ei wyneb yn ystod adwaith gydag ocsigen o'r aer. Er mwyn atal yr adwaith caiff y metel ei storio o dan olew paraffin sy'n cadw'r aer i ffwrdd.

## Cyfeiriadau

 *Eginyn erthygl sydd uchod am **gemeg**. Gallwch helpu Wicipedia drwy ychwanegu ato.*

Wiciadur
Chwiliwch am rwbidiwm
yn Wiciadur.