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Hydrogen



Name Hydrogen
Atomic Number 1
Atomic Weight 1.0079
Symbol H
Melting Point ( °C ) -259
Boiling Point ( °C ) -253
Density (g/cm3) 0.09
Earth crust (%) 0.14
Discovery (Year) 1776
Group 1
Electron configuration 1s1
Ionization energy (eV) 13.5984

Hydrogen is the first element listed in the periodic table. Even though hydrogen is placed above group 1, it does not belong to the Alkali metal family.It is the most abundant element in the universe and is composed of a single proton and a single electron. Many scientists estimated that 90 percent of the universe is made up hydrogen.<ref> Winter, M.“Hydrogen: the essentials”. WebElements: the periodic table on the web . 1993-2009. February 5, 2009, from http://www.webelements.com/hydrogen/</ref>



Discovery

Many scientists had been producing hydrogen for many centuries without ever recognizing it as an element. However during 1766, Hydrogen was recognized as a distinct element by Henry Cavendish. Cavendish noticed that a gas was produced when zinc or iron is dropped into an acid and called it "Inflammable air".<ref> Maxwell, Jeffrey (2007). "Wolfram Research." Retrieved February 5, 2009, from http://scienceworld.wolfram.com/biolgraphy/Cavendish.html</ref> That inflammable gas was later named hydrogen by Antoine Lavoisier in 1783.<ref> “Discovery of Hydrogen and Its Isotopes”.Informplease.2007.Retrieved February 5, 2009, from http://www.infoplease.com/ce6/sci/A0858723.html</ref> In his early experimentation, Cavendish discovered that when hydrogen is combine with oxygen and spark it create water. During his experimentation Cavendish had also discovered that water is composed of two hydrogen, but failed to realize that oxygen is the only portion of air that bonded with hydrogen.

Isotopes

There are three types of hydrogen isotopes. The most common isotope of hydrogen is Protium, which has a mass no. 1 and atomic mass of 1.007822. The nucleus of protium is a proton.<ref> “The Isotopes and Forms”.Informplease.2007.Retrieved February 5, 2009, from http://www.infoplease.com/ce6/sci/A0858719.html</ref> The second isotope is Deuterium, which has a mass no. 2 and atomic mass 2.0140. The nucleus of Deuterium is called the deuteron, which consist of a proton and a neutron.<ref> “The Isotopes and Forms”.Informplease.2007.Retrieved February 5, 2009, from. http://www.infoplease.com/ce6/sci/A0858719.html</ref> Deuterium is often represented in chemical formulas by the symbol D. The two isotopes are found in atmospheric hydrogen with the proportion of 1 atom of deuterium to every 6700 atoms of protium.<ref> “The Isotopes and Forms”.Informplease.2007.Retrieved February 5, 2009, from. http://www.infoplease.com/ce6/sci/A0858719.html</ref> Tritium the third hydrogen isotope has a mass no. 3 and atomic mass of 3.016. Tritium is a radioactive gas with a half-life of about 12 ¼ years. <ref> “The Isotopes and Forms”.Informplease.2007.Retrieved February 5, 2009, from http://www.infoplease.com/ce6/sci/A0858719.html</ref>Tritium is often represented in chemical formulas by the symbol T. Tritium is also produced in nuclear reactors and occurs to a very limited extent in atmospheric hydrogen.

Compounds

On earth, hydrogen is bonded with oxygen in water, but it is also present in organic matter that includes plants, coal and others. <ref> Fendt, W. “Hydrogen” 2003. February 5, 2009, from http://periodic.lanl.gov/elements/1.html</ref> Hydrogen is also present in the planet’s atmosphere as gas.Hydrogen can also form bonds with other elements in many different ways. This element can form the hydride ion (H-) by accepting an electron.<ref> “Hydrogen”.2007. Retrieved February 5, 2009, from http://www.uncp.edu/home/mcclurem/ptable/h.htm</ref> There are two general types of Hydrides; those are saline hydrides and metallic hydrides.<ref> “Hydrogen”.2007. Retrieved February 5, 2009, from http://www.uncp.edu/home/mcclurem/ptable/h.htm</ref> The saline hydrides are formed with alkali metals and other heavier members of the alkaline earth metals. Saline hydrides are ionic substance composed of positive metal cations and negative hydride ions. Metallic hydrides are often referred to as the interstitial hydrides because it is believed that the hydride ions may occupy the intersticies between the atoms.<ref> “Hydrogen”.2007. Retrieved February 5, 2009, from http://www.uncp.edu/home/mcclurem/ptable/h.htm</ref> Hydrogen can also combine with many nonmetals to form compounds that are described as covalent.<ref> “Hydrogen”.2007. Retrieved February 5, 2009, from http://www.uncp.edu/home/mcclurem/ptable/h.htm</ref> Hydrogen has the ability to form extensive series of compound with hydrocarbon. Hydrogen can also be found combined with oxygen in compounds such as water and hydrogen peroxide. Boron or boranes can also form an extensive series of compounds with hydrogen.<ref> “Hydrogen”.2007. Retrieved February 5, 2009, from http://www.uncp.edu/home/mcclurem/ptable/h.htm</ref>

Importance in Bohr Model

Main article: Bohr Model

The Bohr Model was proposed in 1915. CITATION REQUIRED During 1913, Niels Bohr, a physicist, managed to explain the spectrum of atomic hydrogen with the help of Rutherford’s description of the atom. <ref> Fendt, W. “Bohr's Theory of the Hydrogen Atom” May 30, 1999. February 5, 2009, from http://www.walter-fendt.de/ph11e/bohrh.htm</ref> The key constituent of the Bohr atomic model is the energy of the electrons are restricted to certain discrete values; that is, the energy is quantized. This means that only certain orbits with certain radii are allowed; orbits in between simply don't exist. CITATION REQUIRED


Hydrogen ion is recommended by IUPAC as a general term for all ions of hydrogen and its isotopes.[1] Depending on the charge of the ion, two different classes can be distinguished: positively charged ions and negatively charged ions.

The formula H+·H2O is also commonly written as H3O+ and denotes the hydronium or oxonium ion. The amount of hydrogen ion present in a water solution is used as a measure of the acidity of a substance; the higher the concentration of hydrogen ion the more acidic the solution and the lower the pH.


Further Reading

  1. http://www.rsc.org/chemsoc/visualelements/pages/pdf/hydrogen.PDF

References

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