2 - Helium noble gas
Discovered by Pierre Janssen in 1868
- Atomic Radius (Å)
Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.
| Shell | Electrons | Orbitals |
|---|---|---|
| 1 | 2 | 2 in 1s |
4 u
Atomic Mass
0.49 Å
Atomic Radius
4.22 K
Boiling Point
0.28 Å
Covalent Radius
1.79e-4 g/cm³
Density
-4.80e+1
Electron Affinity
24.59 eV
First Ionization Energy
1
Number of Shells
2
Atomic Number
2
Electron Shell Occupations
