Radium (Ra, Z = 88)
Métal alcalino-terreux Bloc s Groupe 2 Période 7 Solide (CNTP)
Radium is a chemical element with symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is almost colorless, but it readily combines with nitrogen (rather than oxygen) on exposure to air, forming a black surface layer of radium nitride (Ra3N2).
Découvreur : Pierre Curie
Propriétés physiques
- Masse atomique standard
- 226,0 u
- Densité
- 5,500 g/cm³
- Point de fusion
- 1 233,0 K
- Point d'ébullition
- 2 010,0 K
- Chaleur molaire
- —
- Électronégativité (Pauling)
- 0,9000
- Affinité électronique
- 9,649 kJ/mol
- Énergies d'ionisation
- 509 ; 979 kJ/mol
- Configuration électronique
- [Rn] 7s2
- Électrons par couche
- K : 2 · L : 8 · M : 18 · N : 32 · O : 18 · P : 8 · Q : 2
- Aspect
- silvery white metallic
Correspondance ANU historique / conjectural
Comptage de la Chimie Occulte (1908) : 4 087 ANU (atomes ultimes), soit N/18 = 227,06 — masse « noologique » à comparer à la masse standard 226,000 u et à l'isotope dominant 228Ra. Coefficient k(Z) = 0,887
Matériel historique et conjectural — voir la page Pont ANU ↔ Nucléides.
Isotopes (35)
| Nucléide | A | N | Masse (u) | Abondance (%) | Demi-vie | Spin | Parité | Magique |
|---|---|---|---|---|---|---|---|---|
| 201Ra | 201 | 113 | 201,012815 | — | 20 ms | 3/2 | ⁻ | — |
| 202Ra | 202 | 114 | 202,009742 | — | 4.1 ms | 0 | ⁺ | — |
| 203Ra | 203 | 115 | 203,009234 | — | 36 ms | 3/2 | ⁻ | — |
| 204Ra | 204 | 116 | 204,006507 | — | 60 ms | 0 | ⁺ | — |
| 205Ra | 205 | 117 | 205,006231 | — | 220 ms | 3/2 | ⁻ | — |
| 206Ra | 206 | 118 | 206,003828 | — | 240 ms | 0 | ⁺ | — |
| 207Ra | 207 | 119 | 207,003772 | — | 1.38 s | 5/2 | ⁻ | — |
| 208Ra | 208 | 120 | 208,001855 | — | 1.11 s | 0 | ⁺ | — |
| 209Ra | 209 | 121 | 209,001995 | — | 4.71 s | 5/2 | ⁻ | — |
| 210Ra | 210 | 122 | 210,000475 | — | 4 s | 0 | ⁺ | — |
| 211Ra | 211 | 123 | 211,000893 | — | 12.6 s | 5/2 | ⁻ | — |
| 212Ra | 212 | 124 | 211,999787 | — | 13 s | 0 | ⁺ | — |
| 213Ra | 213 | 125 | 213,000371 | — | 2.73 min | 1/2 | ⁻ | — |
| 214Ra | 214 | 126 | 214,000100 | — | 2.437 s | 0 | ⁺ | N magique |
| 215Ra | 215 | 127 | 215,002718 | — | 1.669 ms | 9/2 | ⁺ | — |
| 216Ra | 216 | 128 | 216,003534 | — | 172 ns | 0 | ⁺ | — |
| 217Ra | 217 | 129 | 217,006323 | — | 1.95 µs | 9/2 | ⁺ | — |
| 218Ra | 218 | 130 | 218,007134 | — | 25.91 µs | 0 | ⁺ | — |
| 219Ra | 219 | 131 | 219,010085 | — | 9 ms | 7/2 | — | |
| 220Ra | 220 | 132 | 220,011028 | — | 18.1 ms | 0 | ⁺ | — |
| 221Ra | 221 | 133 | 221,013917 | — | 25 s | 5/2 | ⁻ | — |
| 222Ra | 222 | 134 | 222,015373 | — | 33.6 s | 0 | ⁺ | — |
| 223Ra | 223 | 135 | 223,018501 | — | 11.4352 j | 3/2 | ⁺ | — |
| 224Ra | 224 | 136 | 224,020210 | — | 3.6316 j | 0 | ⁺ | — |
| 225Ra | 225 | 137 | 225,023611 | — | 14.82 j | 1/2 | ⁻ | — |
| 226Ra | 226 | 138 | 226,025408 | — | 1.6 ka | 0 | ⁺ | — |
| 227Ra | 227 | 139 | 227,029176 | — | 42.2 min | 3/2 | ⁺ | — |
| 228Ra | 228 | 140 | 228,031069 | — | 5.75 an | 0 | ⁺ | — |
| 229Ra | 229 | 141 | 229,034957 | — | 4 min | 5/2 | — | |
| 230Ra | 230 | 142 | 230,037055 | — | 93 min | 0 | ⁺ | — |
| 231Ra | 231 | 143 | 231,041027 | — | 104 s | 5/2 | ⁺ | — |
| 232Ra | 232 | 144 | 232,043475 | — | 4 min | 0 | ⁺ | — |
| 233Ra | 233 | 145 | 233,047595 | — | 30 s | 1/2 | ⁺ | — |
| 234Ra | 234 | 146 | 234,050382 | — | 30 s | 0 | ⁺ | — |
| 235Ra | 235 | 147 | 235,054890 | — | — | 5/2 | ⁺ | — |
Liseré coloré en première colonne : vert = stable, jaune = demi-vie > 1 an, orange > 1 jour, rouge < 1 jour.