H₂ Or as It's Better Known, HYDROGEN 

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Mass: 2.0g

Melting Point: -259 degrees C

Boiling Point: -252 degrees C

Density: 0.07(measured at boiling point)

Hydrogen is a diatomic element, and therefore a compound with itself. Hydrogen is most commonly known as part of the compound H2O, when hydrogen burns to make water. In fact, the name Hydrogen is derived from the Greek word meaning "maker of water". Hydrogen is incredibly abundant in the Earth, because it occurs in all carbon compounds, as well as glaciers, lakes, oceans, and the atmosphere. Although it is so abundant, Hydrogen makes up only 0.14% of the earth's crust by weight. When Hydrogen was first "discovered", it was confused with other flammable gasses, but in 1766, Henry Cavendish distinguished Hydrogen (then called flammable air) from other flammable gasses by its density and the amount created with the combination of a metal and an acid. Antione-Laurent Lavoisier created the name Hydrogène. Hydrogen can be collected when an acid and a metal are combined, and is tested for by holding a lighted splint over the gas container held the right way up, allowing the gas to escape. Hydrogen is flammable and so produces a bang and short lived flames when lighted. 

The Structure of H₂ and the Chemical Properties of H₂