by Alison Bowler

Created on: May 25, 2009   Last Updated: August 13, 2011

Hydrogen

Symbol: H

Atomic Number: 1

Atomic Mass: 1.00794 amu (atomic mass units)

Melting Point: minus 259.14°C (14.009985 K, minus 434.45203°F)

Boiling Point: minus 252.87°C (20.280005 K, minus 423.166°F)

Number of Protons: 1

Number of Electrons: 1

Number of Neutrons: 0

Classification: Non-metal

Crystal Structure: Hexagonal

Density @ 293 K: 0.00008988 grams per cubic centimeter

Color: colorless

The discovery of the element hydrogen is credited to the British scientist Henry Cavendish in 1766. However, other scientists had produced the gas before this date. There are written records detailing the production of a gas, which could only be hydrogen, by Robert Boyle in 1671 when he was working with metals and acids. The name hydrogen comes from the two Greek words “hydro”, which means water and “genes” meaning forming.

The element is found in group 1 and period 1 of the periodic table. It is the only non-metal found in group 1. All the other elements in group 1 are alkali metals. Hydrogen is the simplest of all the elements in the periodic table consisting of a single electron and a single proton. It is also the most abundant element in the universe. About 90% of the visible universe is composed of hydrogen. Most stars use hydrogen as a fuel source to produce energy in a process known as nuclear fusion. Our own sun has sufficient hydrogen to continue producing energy for the next 5 billion years.

There are two naturally occurring stable isotopes of hydrogen hydrogen-1 (99.985%) and hydrogen-2 (0.015%). Unlike all other elements, the different isotopes of hydrogen have been given individual names. Hydrogen-1 is known as protium but is more commonly just called hydrogen, hydrogen-2 is called deuterium and hydrogen-3 is called tritium. Tritium is an unstable beta emitter, which has a half-life of 12.3 years. Deuterium was discovered in 1932 and tritium in 1934. More recently, three other isotopes have been discovered hydrogen-4, hydrogen-5 and hydrogen-6 these all have extremely short half-lives and decay by neutron emission. The recently discovered isotopes of hydrogen have not been given separate names.

Di-protium oxide (H2O), better known as water, is essential to all life on earth. Other important hydrogen compounds include sugar (C22H22O11), hydrogen peroxide (H2O2) and methane (CH4). Ammonia (NH3) is produced by the Haber process, which combines hydrogen with nitrogen from the air. Hydrogen is used in the hydrogenation

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