Helium vs Meitnerium
| Property | He Helium | Mt Meitnerium |
|---|---|---|
| Atomic number | 2 | 109 |
| Symbol | He | Mt |
| Name | Helium | Meitnerium |
| Category | noble-gas | transition-metal |
| Standard Atomic Weight | 4.002602 u | 278 u |
| Period | 1 | 7 |
| Group | 18 | 9 |
| Block | s | s |
| Phase at STP | gas | N/A |
| Electron configuration | 1s2 | [Rn]7s25f146d7(calculated) |
| Oxidation states | [0] | [1, 3, 4, 6, 8, 9] |
| Electronegativity (Pauling) | N/A | N/A |
| Electron affinity | -0.5 eV | 1.7 eV |
| Density | 0.1785 kg/m³ | 3.740000e+4 kg/m³ |
| Melting point | -272.2 °C | -273.15 °C |
| Boiling point | -268.93 °C | -273.15 °C |
| Discovery year | 1868 | 1982 |