Calcium vs Protactinium
| Property | Ca Calcium | Pa Protactinium |
|---|---|---|
| Atomic number | 20 | 91 |
| Symbol | Ca | Pa |
| Name | Calcium | Protactinium |
| Category | alkaline-earth-metal | actinide |
| Standard Atomic Weight | 40.078 u | 231.03588 u |
| Period | 4 | 7 |
| Group | 2 | N/A |
| Block | s | s |
| Phase at STP | solid | solid |
| Electron configuration | [Ar]4s2 | [Rn]7s25f26d1 |
| Oxidation states | [1, 2] | [2, 3, 4, 5] |
| Electronegativity (Pauling) | 1 | 1.5 |
| Electron affinity | 0.0245 eV | 0.123 eV |
| Density | 1540 kg/m³ | 1.537000e+4 kg/m³ |
| Melting point | 841.85 °C | 1571.85 °C |
| Boiling point | 1483.85 °C | -273.15 °C |
| Discovery year | 1808 | 1913 |