From Wikipedia, the free encyclopediaHelium 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. | |||||
Helium in the periodic table | |||||
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Symbol | He | ||||
Atomic number | 2 | ||||
Group | 18 | ||||
Period | 1 | ||||
Block | s | ||||
Element category | Noble Gas | ||||
Physical properties | |||||
Phase at STP | Gas | ||||
Density | 0.1786 g/cm3 | ||||
Atomic weight | 4.0026 u | ||||
Melting point | 0.95 K -272.2 °C -457.96 °F | ||||
Boiling point | 4.222 K -268.928 °C -452.0704 °F | ||||
Atomic properties | |||||
Electronegativity (Pauling Scale) | |||||
Electron affinity | -48 kJ/mol | ||||
Oxidation states | 0 | ||||
Ionization energies |
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Electron configuration | |||||
Elektronkonfiguration (shorthand) | 1s2 | ||||
Electron configuration | 1s2 | ||||
Electrons per shell | 2 | ||||
History | |||||
Discovered | 1868 | ||||
Discovered by | Pierre Janssen Norman Lockyer |