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Radium |
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Pronunciation | (RAY-dee-əm) |
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Appearance | sillery white metallic |
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Mass number | [226] |
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Radium in the periodic cairt |
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Ba ↑ Ra ↓ (Ubn) |
francium ← radium → actinium |
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Atomic nummer (Z) | 88 |
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Group | group 2 (alkaline yird metals) |
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Period | period 7 |
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Block | s-block |
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Element category | Alkaline yird metal |
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Electron confeeguration | [Rn] 7s2 |
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Electrons per shell | 2, 8, 18, 32, 18, 8, 2 |
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Pheesical properties |
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Phase at STP | solit |
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Meltin pynt | 1233 K (960 °C, 1760 °F) (disputed) |
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Bylin pynt | 2010 K (1737 °C, 3159 °F) |
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Density (near r.t.) | 5.5 g/cm3 |
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Heat o fusion | 8.5 kJ/mol |
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Heat o vapourisation | 113 kJ/mol |
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Vapour pressur
P (Pa) |
1 |
10 |
100 |
1 k |
10 k |
100 k |
at T (K) |
819 |
906 |
1037 |
1209 |
1446 |
1799 |
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Atomic properties |
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Oxidation states | +2 strangly basic expectit |
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Electronegativity | Pauling scale: 0.9 |
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Ionisation energies | - 1st: 509.3 kJ/mol
- 2nd: 979.0 kJ/mol
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Covalent radius | 221±2 pm |
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Van der Waals radius | 283 pm |
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Spectral lines o radium |
Ither properties |
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Creestal structur | body-centred cubic |
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Thermal conductivity | 18.6 W/(m·K) |
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Electrical resistivity | 1 µΩ·m (at 20 °C) |
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Magnetic orderin | nonmagnetic |
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CAS Nummer | 7440-14-4 |
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History |
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Diskivery | Pierre Curie an Marie Curie (1898) |
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First isolation | Marie Curie (1910) |
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Main isotopes o radium |
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Isotope |
Abundance |
Hauf-life (t1/2) |
Decay mode |
Product |
223Ra |
trace |
11.43 d |
α |
219Rn |
224Ra |
trace |
3.6319 d |
α |
220Rn |
225Ra |
trace |
14.9 d |
β− |
225Ac |
226Ra |
trace |
1600 y |
α |
222Rn |
228Ra |
trace |
5.75 y |
β− |
228Ac |
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| references |