Discovery date : 1895
Discovered by: Sir William Ramsay in London, and independently by Per Teodor Cleve
and Nils Abraham Langlet in Uppsala, Sweden
Origin of the name :The name is derived from the Greek, 'helios' meaning sun,
as it was in the sun's corona
that helium was first detected.
Allotropes : -
~>HELIUM is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements.
| FACT BOX | |||
| Group | 18 | Melting point | Unknown |
| Period | 1 | Boiling point | −268.928°C, −452.07°F, 4.222 K |
| Block | s | Density (g cm−3) | 0.000164 |
| Atomic number | 2 | Relative atomic mass | 4.003 |
| State at 20°C | Gas | Key isotopes | 4He |
| Electron configuration | 1s2 | CAS number | 7440-59-7 |
| ChemSpider ID | 22423 | ChemSpider is a free chemical structure database | |
In 1868, Pierre J. C. Janssen travelled to India to measure the solar spectrum during a total eclipse and observed a new yellow line which indicated a new element. Joseph Norman Lockyer recorded the same line by observing the sun through London smog and, assuming the new element to be a metal, he named it helium.
In 1882, the Italian Luigi Palmieri found the same line the spectrum of gases emitted by Vesuvius, as did the American William Hillebrand in 1889 when he collected the gas given off by the mineral uraninite (UO2) as it dissolves in acid. However, it was Per Teodor Cleve and Nils Abraham Langer at Uppsala, Sweden, in 1895, who repeated that experiment and confirmed it was helium and measured its atomic weight.