Period 1 element (He) is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas series in the periodic table and whose atomic number is 2. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions. Helium was discovered in 1868 by French astronomer Pierre Janssen, who first detected the substance as an unknown yellow spectral line signature in light from a solar eclipse. In 1903, large reserves of helium were found in the natural gas fields of the United States, which is by far the largest
Boiling point boiling point of water" at a standard pressure of 100 kPa (1 bar) is . For comparison, on top of Mount Everest, at elevation, the pressure is about and the boiling point of water is . The Celsius temperature scale was defined until 1954 by two points: 0 °C being defined by the water freezing point and 100 °C being defined by the water boiling point at standard atmospheric pressure. The higher the vapor pressure of a liquid at a given temperature, the lower the normal boiling point (i.e., the boiling point at atmospheric pressure) of the liquid. The vapor