Period 1 element

Period 1 element

A period 1 element is one of the chemical elements in the first row (or period) of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The first period contains fewer elements than any other row in the table, with only two: hydrogen and helium. Helium behaves as a noble gas, and is taken as the end of the row; the next period contains eight elements, as it is not until then that another element behaving as a noble gas occurs. This situation can be explained by modern theories of atomic structure.


A period 1 element is one of the chemical elements in the first row (or "period") of the periodic table of the chemical elements. This first period contains fewer elements than any other row in the table, with only hydrogen and helium. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the 1s orbital. Period 1 elements do not obey the octet rule. The maximum number of electrons that both elements can accommodate is two; an element with a configuration of two elements is called a "duet".



Hydrogen (H) is the chemical element with atomic number 1. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H2. With an atomic mass of 1.00794 amu, hydrogen is the lightest element. [cite web|accessdate=2008-07-15|url=|title=Hydrogen – Energy |publisher=Energy Information Administration ]

Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. [cite web | last=Palmer | first=David | date=November 13, 1997 | url= | title=Hydrogen in the Universe | publisher=NASA | accessdate=2008-02-05 ] 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 almost equally divided between fossil fuel upgrading, such as hydrocracking, and ammonia production, mostly for the fertilizer market. Hydrogen may be produced from water using the process of electrolysis, but this process is significantly more expensive commercially than hydrogen production from natural gas. [cite web | author=Staff | year=2007 | url= | title=Hydrogen Basics — Production | publisher=Florida Solar Energy Center | accessdate=2008-02-05 ]

The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and no neutrons. [cite news|title=Fusion Power Is Still Facing Formidable Difficulties|work=The New York Times|date=1971-03-11|author=Sullivan, Walter] 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. [cite encyclopedia|encyclopedia=Encyclopædia Britannica|date=2008|title=hydrogen] It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules. [cite journal|accessdate=2008-07-15|url=|title=Electron-Driven Acid-Base Chemistry: Proton Transfer from Hydrogen Chloride to Ammonia |work=Science Magazine|date=2008-02-15|volume=319|issue=5865|pages=936–939|doi=10.1126/science.1151614 ] As the only neutral atom for which the Schrödinger equation can be solved analytically, study of the energetics and spectrum of the hydrogen atom has played a key role in the development of quantum mechanics. [cite encyclopedia|encyclopedia=Encyclopædia Britannica|date=2008|title= Time-dependent Schrödinger equation]

The interactions of hydrogen with various metals are very important in metallurgy, as many metals can suffer hydrogen embrittlement, [cite journal | last=Rogers | first=H. C. | title=Hydrogen Embrittlement of Metals | journal=Science | year=1999 | volume=159 | issue=3819 | pages=1057–1064 | doi=10.1126/science.159.3819.1057 | pmid=17775040] and in developing safe ways to store it for use as a fuel. [cite news | last=Christensen | first=C. H. | coauthors=Nørskov, J. K.; Johannessen, T. | date=July 9, 2005 | title=Making society independent of fossil fuels — Danish researchers reveal new technology | publisher=Technical University of Denmark | url= | accessdate=2008-03-28 ] Hydrogen is highly soluble in many compounds composed of rare earth metals and transition metalscite journal | last=Takeshita | first=T. | coauthors=Wallace, W.E.; Craig, R.S. | title=Hydrogen solubility in 1:5 compounds between yttrium or thorium and nickel or cobalt | journal=Inorganic Chemistry | year=1974 | volume=13 | issue=9 | pages=2282–2283 | doi = 10.1021/ic50139a050 ] and can be dissolved in both crystalline and amorphous metals.cite journal | last=Kirchheim | first=R. | coauthors=Mutschele, T.; Kieninger, W | title=Hydrogen in amorphous and nanocrystalline metals | journal=Materials Science and Engineering | year=1988 | volume=99 | pages=457–462 | doi = 10.1016/0025-5416(88)90377-1 ] Hydrogen solubility in metals is influenced by local distortions or impurities in the metal crystal lattice.cite journal | last=Kirchheim | first=R. | title=Hydrogen solubility and diffusivity in defective and amorphous metals | journal=Progress in Materials Science | year=1988 | volume=32 | issue=4 | pages=262–325 | doi = 10.1016/0079-6425(88)90010-2]


Helium (He) is a colorless, odorless, tasteless, non-toxic, inert monatomic chemical element that heads the noble gas series in the periodic table and whose atomic number is 2. [cite web|accessdate=2008-07-15|url=|title=Helium: the essentials |publisher=WebElements ] Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions. [cite web|accessdate=2008-07-15|url=|title=Helium: physical properties |publisher=WebElements ]

Helium was discovered in 1868 by French astronomer Pierre Janssen, who first detected the substance as an unknown yellow spectral line signature in light from a solar eclipse. [cite web|accessdate=2008-07-15|url=|title=Pierre Janssen |publisher=MSN Encarta ] In 1903, large reserves of helium were found in the natural gas fields of the United States, which is by far the largest supplier of the gas. [cite web|accessdate=2008-07-15|url=|title=Where Has All the Helium Gone? |publisher=Bureau of Land Management|date=2007-01-18|author=Theiss, Leslie ] The substance is used in cryogenics, [cite book|title=Cryogenic Engineering: Fifty Years of Progress|author=Timmerhaus, Klaus D.|date=2006-10-06|publisher=Springer|isbn=038733324X] in deep-sea breathing systems, [cite journal|title=Helium voice unscrambling|author=Copel, M.|journal=Audio and Electroacoustics|volume=14|issue=3|date=September 1966|pages=122–126] to cool superconducting magnets, in helium dating, [cite encyclopedia|encyclopedia=Encyclopædia Britannica|date=2008|title=helium dating] for inflating balloons, [cite web|accessdate=2008-07-15|url=|title=How Helium Balloons Work |publisher=How Stuff Works|author=Brain, Marshall ] for providing lift in airships, [cite web|accessdate=2008-07-15|url=|title= The Return of the Blimp |work=Popular Science|date=2008-07-10|author=Jiwatram, Jaya ] and as a protective gas for industrial uses such as arc welding and growing silicon wafers. [cite journal|title=When good GTAW arcs drift; drafty conditions are bad for welders and their GTAW arcs.|journal=Welding Design & Fabrication|date=2005-02-01] Inhaling a small volume of the gas temporarily changes the timbre and quality of the human voice. [cite web|accessdate=2008-07-15|url=|title=Why does inhaling helium make one's voice sound strange? |work=Scientific American|date=2006-09-04|author=Montgomery, Craig ] The behavior of liquid helium-4's two fluid phases, helium I and helium II, is important to researchers studying quantum mechanics and the phenomenon of superfluidity in particular, [cite web|accessdate=2008-07-15|url=|title=Probable Discovery Of A New, Supersolid, Phase Of Matter |publisher=Science Daily|date=2004-09-03 ] and to those looking at the effects that temperatures near absolute zero have on matter, such as with superconductivity. [cite news|title=Scientists See Peril In Wasting Helium; Scientists See Peril in Waste of Helium|work=The New York Times|date=1979-08-21|author= Browne, Malcolm W.]

Helium is the second lightest element and is the second most abundant in the observable universe. [cite web|accessdate=2008-07-15|url=|title=Helium: geological information |publisher=WebElements ] Most helium was formed during the Big Bang, but new helium is being created as a result of the nuclear fusion of hydrogen in stars. [cite web|accessdate=2008-07-15|url=|title=Origin of the chemical elements
work=New Scientist|date=1990-02-03|author=Cox, Tony
] On Earth, helium is relatively rare and is created by the natural decay of some radioactive elements [cite news|title=Helium supply deflated: production shortages mean some industries and partygoers must squeak by.|publisher=Houston Chronicle|date=2006-11-05] because the alpha particles that are emitted consist of helium nuclei. [cite news|title=CALL EARTH'S AGE 2 1/2 BILLION YEARS; Wilkins and Rayton Report to Scientists, at Rochester, on Extensive Study. 'INFANCY' A LONG PERIOD Time Before Maturity Into Cold Planet Put at 700,000,000 Through Atomic Method.|work=The New York Times|date=1936-06-17|author=Laurence, William L.] This radiogenic helium is trapped with natural gas in concentrations of up to seven percent by volume, [cite web|accessdate=2008-07-15|url=|title=Helium a New Target in New Mexico |publisher=American Association of Petroleum Geologists|date=2008-02-02|author=Brown, David ] from which it is extracted commercially by a low-temperature separation process called fractional distillation. [cite news|title=Where Do We Get the Helium We Use?|publisher=The Science Teacher|date=2006-12-01|author=Voth, Greg]

Table of elements

element color legend




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