What is hydrogen ? Hydrogen is the simplest element known to man. Each atom of hydrogen has only one proton. This element is found on the Earth and in the stars as well. It plays an important part in powering the universe through both the proton-proton reaction and carbon-nitrogen cycle. Stellar hydrogen fusion processes release massive amounts of energy by combining hydrogens to form helium. In chemistry hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H2. With an atomic weight of 1.00794, hydrogen is the lightest element. How was hydrogen discovered? Hydrogen gas, H2, was first artificially produced and formally described by T. Von Hohenheim (also known as Paracelsus, 1493–1541) via the mixing of metals with strong acids. He was unaware that the flammable gas produced by this chemical reaction was a new chemical element. In 1671, Robert Boyle rediscovered and described the reaction between iron filings and dilute acids, which results in the production of hydrogen gas. In 1766, Henry Cavendish was the first to recognize hydrogen gas as a discrete substance, by identifying the gas from a metal-acid reaction as "inflammable air" and further finding in 1781 that the gas produces water when burned. He is usually given credit for its discovery as an element. In 1783, Antoine Lavoisier gave the element the name of hydrogen (from the Greek hydro meaning water and genes meaning creator) when he and Laplace reproduced Cavendish's finding that water is produced when hydrogen is burned. Why is hydrogen important? Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Elemental hydrogen is relatively rare on Earth, and is industrially produced from hydrocarbons such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets about equally divided between fossil fuel upgrading (e.g., hydrocracking) and ammonia production (mostly for the fertilizer market). Hydrogen may be produced from water using the process of electrolysis, but this process is presently significantly more expensive commercially than hydrogen production from natural gas. The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and no neutrons. In ionic compounds it can take on either a positive charge (becoming a cation composed of a bare proton) or a negative charge (becoming an anion known as a hydride). Hydrogen can form compounds with most elements and is present in water and most organic compounds. It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules. As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and bonding of the hydrogen atom has played a key role in the development of quantum mechanics. The solubility and characteristics of hydrogen with various metals are very important in metallurgy (as many metals can suffer hydrogen embrittlement) and in developing safe ways to store it for use as a fuel. Hydrogen is highly soluble in many compounds composed of rare earth metals and transition metals and can be dissolved in both crystalline and amorphous metals. Hydrogen solubility in metals is influenced by local distortions or impurities in the metal crystal lattice. Hydrogen gas is highly flammable and will burn at concentrations of 4% or more H2 in air. When mixed with oxygen across a wide range of proportions, hydrogen explodes upon ignition. Hydrogen burns violently in air. It ignites automatically at a temperature of 560 °C. Pure hydrogen-oxygen flames burn in the ultraviolet color range and are nearly invisible to the naked eye. These properties make hydrogen very usable as a fuel. How can we exploit properties of hyrdogen? A hydrogen economy is proposed to solve some of the negative effects of using hydrocarbon fuels in transportation, and other end-use applications where the carbon is released to the atmosphere. In the current hydrocarbon economy, the transportation of people and goods is fueled primarily by petroleum, refined into gasoline and diesel, and natural gas. However, the burning of these hydrocarbon fuels causes the emission of greenhouse gases and other pollutants. Furthermore, the supply of hydrocarbon resources in the world is limited, and the demand for hydrocarbon fuels is increasing, particularly in China, India and other developing countries. Hydrogen has a high energy density by weight. The fuel cell is also more efficient than an internal combustion engine . The internal combustion engine is said to be 20–30% efficient, while the fuel cell is 2-3 times more efficient than an internal combustion engine depending on the fuel cell. Hydrogen facts: Hydrogen is used extensively today to make ammonia, methanol, gasoline, heating oil, and rocket fuel. It is also used to make fertilizers, glass, refined metals, vitamins, cosmetics, semiconductor circuits, soaps, lubricants, cleaners, and even margarine and peanut butter. Hydrogen can fuel today’s internal combustion engine vehicles. Hydrogen can fuel tomorrow’s fuel-cell vehicles. Hydrogen can replace today’s natural gas for heating and cooling homes and powering hot water heaters. Existing wind and hydroelectric plants can produce hydrogen to store energy during off-peak hours. Hydrogen production from hydrocarbons can also produce carbon, which in some forms has ten times the strength of steel. With more research, this carbon could be used for automobile bodies and structural members. Hydrogen properties: General: Name: Hydrogen Symbol: H Group: Non-Metal Atomic weight: 1.0079 Density @ 293 K: 0.0000899 g/cm3 Atomic volume: 14.4 cm3/mol Group: Non-Metal Official discovery: 1766 States: state (s, l, g): g melting point: 14.06 K boiling point: 20.4 K Heat of fusion: 0.05868 kJ/mol Heat of vaporization: 0.44936 kJ/mol Energies: 1st ionization energy: 1312 kJ/mole electronegativity: 2.2 2nd ionization energy: kJ/mole electron affinity: 72.7711 kJ/mole 3rd ionization energy: kJ/mole Specific heat: 14.304 J/gK heat atomization: 218 kJ/mole atoms Oxidation & Electrons: Shells: 1 electron configuration: 1s1 minimum oxidation number: -1 maximum oxidation number: 1 min. common oxidation no.: -1 max. common oxidation no.: 1 Appearance & Characteristics: structure: hcp: hexagonal close pkd color: colorless uses: rocket fuel toxicity: hardness: mohs characteristics: diatomic,dens Reactions: reaction with air: vigorous, =>H2O reaction with 6M HCl: none reaction with 6M HCl: none reaction with 15M HNO3: none reaction with 6M NaOH: none Other Forms: number of isotopes: 3 hydride(s): H2 oxide(s): H2O chloride(s): HCl Radius: ionic radius (2- ion): pm ionic radius (1- ion): pm atomic radius: 37.1 pm ionic radius (1+ ion): pm ionic radius (2+ ion): pm ionic radius (3+ ion): pm Conductivity: thermal conductivity: 0.18 J/m-sec-deg electrical conductivity: 1/mohm-cm polarizability: 0.7 A^3 Abundance: source: Water, methane rel. abund. solar system: 10.446 log abundance earth's crust: 3.1 log cost, pure: 12 $/100g cost, bulk: $/100g Sources: http://www.chemicool.com/elements/hydrogen.html#energies http://periodic.lanl.gov/elements/1.html http://en.wikipedia.org/wiki/Hydrogen http://en.wikipedia.org/wiki/Hydrogen_fuel http://www.eia.doe.gov/kids/energyfacts/sources/IntermediateHydrogen.html