Atomic Number: 1
Relative Atomic Mass: 1.008

Appearance
Hydrogen is a colourless gas

Source
Hydrogen is found in the Sun as a source for its nuclear reaction. It is the most abundant element in the Universe. On Earth, hydrogen is found in the greatest quantities in water. The atmosphere contains less than 1 part per million of hydrogen.

Commercially, hydrogen is produced by several methods. These are:

electrolysis of water
displacement from acids by certain metals
decomposition of hydrocarbons
reaction of steam on heated carbon
action of sodium or potassium hydroxide on aluminium


Uses
Large quantities of hydrogen are used in the Haber Process to produce ammonia, and in the hydogenation of fats and oils. It is also used in welding and the reduction of metal ores. Liquid hydrogen is very important in cryogenics and superconductivity studies as its melting point is just above absolute zero.

Other Information
Hydrogen has three isotopes - Protium, Deuterium and Tritium. Protium is the most abundant isotope, and is the the one that is ordinarily referred to when hydrogen is mentioned. Its atomic mass is 1. Deuterium has an atomic mass of 2 and was discovered in 1932. Tritium is the least common and most unstable isotope, its half-life is about 12½ years. Tritium is used in hydrogen bombs, nuclear reactors and luminous paints.