Radium vs Actinium
Side-by-side comparison of Radium (Ra, element 88) and Actinium (Ac, element 89) by atomic structure and physical properties.
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| Atomic number | 88 | 89 |
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| Symbol | Ra | Ac |
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| Name | Radium | Actinium |
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| Category | alkaline-earth-metal | actinide |
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| Standard Atomic Weight | 226 u | 227 u |
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| Period | 7 | 7 |
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| Group | 2 | N/A |
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| Block | s | f |
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| Phase at STP | Solid | Solid |
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| Electron configuration | [Rn]7s2 | [Rn]6d17s2 |
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| Oxidation states | [2] | [3] |
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| Electronegativity (Pauling) | 0.9 | 1.1 |
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| Electron affinity | 0.1 eV | 0.35 eV |
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| Density | 5000 kg/m³ | 1.007e+4 kg/m³ |
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| Melting point | 699.85 °C | 1050.85 °C |
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| Boiling point | 1736.85 °C | 3197.85 °C |
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| Discovery year | 1898 | 1899 |
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Key Differences
| Ra Radium | Ac Actinium |
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| Standard Atomic Weight | 226 u ↓ lower | 227 u ↑ higher |
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| Density | 5000 kg/m³ ↓ lower | 1.007e+4 kg/m³ ↑ higher |
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| Melting point | 699.85 °C ↓ lower | 1050.85 °C ↑ higher |
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| Boiling point | 1736.85 °C ↓ lower | 3197.85 °C ↑ higher |
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| Electronegativity (Pauling) | 0.9 ↓ lower | 1.1 ↑ higher |
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| Electron affinity | 0.1 eV ↓ lower | 0.35 eV ↑ higher |
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| Block | s | f |
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| Category | alkaline-earth-metal | actinide |
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| Electron configuration | [Rn]7s2 | [Rn]6d17s2 |
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| Discovery year | 1898 | 1899 |
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