Potassium vs Calcium
Side-by-side comparison of Potassium (K, element 19) and Calcium (Ca, element 20) by atomic structure and physical properties.
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| Atomic number | 19 | 20 |
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| Symbol | K | Ca |
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| Name | Potassium | Calcium |
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| Category | alkali-metal | alkaline-earth-metal |
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| Standard Atomic Weight | 39.0983 u | 40.078 u |
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| Period | 4 | 4 |
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| Group | 1 | 2 |
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| Block | s | s |
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| Phase at STP | Solid | Solid |
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| Electron configuration | [Ar]4s1 | [Ar]4s2 |
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| Oxidation states | [-1, 1] | [1, 2] |
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| Electronegativity (Pauling) | 0.82 | 1 |
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| Electron affinity | 0.5014 eV | 0.024551 eV |
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| Density | 890 kg/m³ | 1540 kg/m³ |
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| Melting point | 63.38 °C | 841.85 °C |
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| Boiling point | 758.85 °C | 1483.85 °C |
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| Discovery year | 1807 | 1808 |
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Key Differences
| K Potassium | Ca Calcium |
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| Standard Atomic Weight | 39.0983 u ↓ lower | 40.078 u ↑ higher |
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| Density | 890 kg/m³ ↓ lower | 1540 kg/m³ ↑ higher |
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| Melting point | 63.38 °C ↓ lower | 841.85 °C ↑ higher |
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| Boiling point | 758.85 °C ↓ lower | 1483.85 °C ↑ higher |
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| Electronegativity (Pauling) | 0.82 ↓ lower | 1 ↑ higher |
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| Electron affinity | 0.5014 eV ↑ higher | 0.024551 eV ↓ lower |
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| Group | 1 | 2 |
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| Category | alkali-metal | alkaline-earth-metal |
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| Electron configuration | [Ar]4s1 | [Ar]4s2 |
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| Discovery year | 1807 | 1808 |
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