2He4.0026
Helium (He)
Element 2 Ā· Noble gas
Helium (He) is a chemical element with atomic number 2. It is classified as a noble gas in period 1, group 18 of the periodic table (the s-block). Its standard atomic weight is 4.0026 u and its ground-state electron configuration is 1sĀ².
Helium facts
| Atomic number (Z) | 2 |
|---|---|
| Symbol | He |
| Standard atomic weight | 4.0026 u |
| Category | Noble gas |
| Group | 18 |
| Period | 1 |
| Block | s-block |
| Electron configuration | 1sĀ² |
| Electronegativity (Pauling) | ā |
| State at 20 Ā°C | Gas |
| Protons / electrons | 2 / 2 |
| Neutrons (most common isotope, approx.) | 2 |
| Molar mass | 4.0026 g/mol |