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 periodic (recurring) 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. This situation can be explained by modern theories of atomic structure. In a quantum mechanical description of atomic structure, this period corresponds to the filling of the 1s orbital. Period 1 elements obey the duet rule in that they need two electrons to complete their valence shell. The maximum number of electrons that these elements can accommodate is two, both in the 1s orbital. Therefore, period 1 can have only two elements.

Periodic trends

All other periods in the period table contain at least 8 elements, and it is often helpful to consider periodic trends across the period. However, period 1 contains only two elements, so this concept does not apply here.

In terms of vertical trends down groups, helium can be seen as a typical noble gas at the head of Group 18, but as discussed below, hydrogen's chemistry is unique and it is not easily assigned to any group.

Position of period 1 elements in the periodic table

Although both hydrogen and helium are in the s-block, neither of them behaves similarly to other s-block elements. Their behaviour is so different from the other s-block elements that there is considerable disagreement over where these two elements should be placed in the periodic table.

Hydrogen is sometimes placed above lithium,[1] above carbon,[2] above fluorine,[2][3] above both lithium and fluorine (appearing twice),[4] or left floating above the other elements and not assigned to any group[4] in the periodic table.

Helium is almost always placed above neon (which is in the p-block) in the periodic table as a noble gas,[1] although it is occasionally placed above beryllium due to their similar electron configuration.[5]

Elements

Chemical element Chemical series Electron configuration
1 H Hydrogen Reactive nonmetal 1s1
2 He Helium Noble gas 1s2

Hydrogen

Hydrogen discharge tube
Hydrogen discharge tube
Deuterium discharge tube
Deuterium discharge tube

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.[6]

Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass.[7] 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.[8]

The most common naturally occurring isotope of hydrogen, known as protium, has a single proton and no neutrons.[9] 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.[10] It plays a particularly important role in acid-base chemistry, in which many reactions involve the exchange of protons between soluble molecules.[11] 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.[12]

The interactions of hydrogen with various metals are very important in metallurgy, as many metals can suffer hydrogen embrittlement,[13] and in developing safe ways to store it for use as a fuel.[14] Hydrogen is highly soluble in many compounds composed of rare earth metals and transition metals[15] and can be dissolved in both crystalline and amorphous metals.[16] Hydrogen solubility in metals is influenced by local distortions or impurities in the metal crystal lattice.[17]

Helium

Helium discharge tube
Helium discharge tube

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.[18] Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme conditions.[19]

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.[20] 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.[21] The substance is used in cryogenics,[22] in deep-sea breathing systems,[23] to cool superconducting magnets, in helium dating,[24] for inflating balloons,[25] for providing lift in airships,[26] and as a protective gas for industrial uses such as arc welding and growing silicon wafers.[27] Inhaling a small volume of the gas temporarily changes the timbre and quality of the human voice.[28] 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,[29] and to those looking at the effects that temperatures near absolute zero have on matter, such as with superconductivity.[30]

Helium is the second lightest element and is the second most abundant in the observable universe.[31] 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.[32] On Earth, helium is relatively rare and is created by the natural decay of some radioactive elements[33] because the alpha particles that are emitted consist of helium nuclei. This radiogenic helium is trapped with natural gas in concentrations of up to seven percent by volume,[34] from which it is extracted commercially by a low-temperature separation process called fractional distillation.[35]

References

  1. ^ a b "International Union of Pure and Applied Chemistry > Periodic Table of the Elements". IUPAC. Retrieved 2011-05-01.
  2. ^ a b Cronyn, Marshall W. (August 2003). "The Proper Place for Hydrogen in the Periodic Table". Journal of Chemical Education. 80 (8): 947–951. Bibcode:2003JChEd..80..947C. doi:10.1021/ed080p947.
  3. ^ Vinson, Greg (2008). "Hydrogen is a Halogen". HydrogenTwo.com. Archived from the original on January 10, 2012. Retrieved January 14, 2012.
  4. ^ a b Kaesz, Herb; Atkins, Peter (November–December 2003). "A Central Position for Hydrogen in the Periodic Table". Chemistry International. International Union of Pure and Applied Chemistry. 25 (6): 14. Retrieved January 19, 2012.
  5. ^ Winter, Mark (1993–2011). "Janet periodic table". WebElements. Archived from the original on April 6, 2012. Retrieved January 19, 2012.
  6. ^ "Hydrogen – Energy". Energy Information Administration. Retrieved 2008-07-15.
  7. ^ Palmer, David (November 13, 1997). "Hydrogen in the Universe". NASA. Retrieved 2008-02-05.
  8. ^ Staff (2007). "Hydrogen Basics — Production". Florida Solar Energy Center. Retrieved 2008-02-05.
  9. ^ Sullivan, Walter (1971-03-11). "Fusion Power Is Still Facing Formidable Difficulties". The New York Times.
  10. ^ "hydrogen". Encyclopædia Britannica. 2008.
  11. ^ Eustis, S. N.; Radisic, D.; Bowen, K. H.; Bachorz, R. A.; Haranczyk, M.; Schenter, G. K.; Gutowski, M. (2008-02-15). "Electron-Driven Acid-Base Chemistry: Proton Transfer from Hydrogen Chloride to Ammonia". Science. 319 (5865): 936–939. Bibcode:2008Sci...319..936E. doi:10.1126/science.1151614. PMID 18276886.
  12. ^ "Time-dependent Schrödinger equation". Encyclopædia Britannica. 2008.
  13. ^ Rogers, H. C. (1999). "Hydrogen Embrittlement of Metals". Science. 159 (3819): 1057–1064. Bibcode:1968Sci...159.1057R. doi:10.1126/science.159.3819.1057. PMID 17775040.
  14. ^ Christensen, C. H.; Nørskov, J. K.; Johannessen, T. (July 9, 2005). "Making society independent of fossil fuels — Danish researchers reveal new technology". Technical University of Denmark. Archived from the original on January 7, 2010. Retrieved 2008-03-28.
  15. ^ Takeshita, T.; Wallace, W.E.; Craig, R.S. (1974). "Hydrogen solubility in 1:5 compounds between yttrium or thorium and nickel or cobalt". Inorganic Chemistry. 13 (9): 2282–2283. doi:10.1021/ic50139a050.
  16. ^ Kirchheim, R.; Mutschele, T.; Kieninger, W (1988). "Hydrogen in amorphous and nanocrystalline metals". Materials Science and Engineering. 99: 457–462. doi:10.1016/0025-5416(88)90377-1.
  17. ^ Kirchheim, R. (1988). "Hydrogen solubility and diffusivity in defective and amorphous metals". Progress in Materials Science. 32 (4): 262–325. doi:10.1016/0079-6425(88)90010-2.
  18. ^ "Helium: the essentials". WebElements. Retrieved 2008-07-15.
  19. ^ "Helium: physical properties". WebElements. Retrieved 2008-07-15.
  20. ^ "Pierre Janssen". MSN Encarta. Archived from the original on 2009-10-29. Retrieved 2008-07-15.
  21. ^ Theiss, Leslie (2007-01-18). "Where Has All the Helium Gone?". Bureau of Land Management. Archived from the original on 2008-07-25. Retrieved 2008-07-15.
  22. ^ Timmerhaus, Klaus D. (2006-10-06). Cryogenic Engineering: Fifty Years of Progress. Springer. ISBN 0-387-33324-X.
  23. ^ Copel, M. (September 1966). "Helium voice unscrambling". Audio and Electroacoustics. 14 (3): 122–126. doi:10.1109/TAU.1966.1161862.
  24. ^ "helium dating". Encyclopædia Britannica. 2008.
  25. ^ Brain, Marshall. "How Helium Balloons Work". How Stuff Works. Retrieved 2008-07-15.
  26. ^ Jiwatram, Jaya (2008-07-10). "The Return of the Blimp". Popular Science. Retrieved 2008-07-15.
  27. ^ "When good GTAW arcs drift; drafty conditions are bad for welders and their GTAW arcs". Welding Design & Fabrication. 2005-02-01.
  28. ^ Montgomery, Craig (2006-09-04). "Why does inhaling helium make one's voice sound strange?". Scientific American. Retrieved 2008-07-15.
  29. ^ "Probable Discovery Of A New, Supersolid, Phase Of Matter". Science Daily. 2004-09-03. Retrieved 2008-07-15.
  30. ^ Browne, Malcolm W. (1979-08-21). "Scientists See Peril In Wasting Helium; Scientists See Peril in Waste of Helium". The New York Times.
  31. ^ "Helium: geological information". WebElements. Retrieved 2008-07-15.
  32. ^ Cox, Tony (1990-02-03). "Origin of the chemical elements". New Scientist. Retrieved 2008-07-15.
  33. ^ "Helium supply deflated: production shortages mean some industries and partygoers must squeak by". Houston Chronicle. 2006-11-05.
  34. ^ Brown, David (2008-02-02). "Helium a New Target in New Mexico". American Association of Petroleum Geologists. Retrieved 2008-07-15.
  35. ^ Voth, Greg (2006-12-01). "Where Do We Get the Helium We Use?". The Science Teacher.

Further reading

Index of chemistry articles

Chemistry (from Egyptian kēme (chem), meaning "earth") is the physical science concerned with the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions.Below is a list of chemistry-related articles. Chemical compounds are listed separately at list of organic compounds, list of inorganic compounds or list of biomolecules.

Periodic table

The periodic table, also known as the periodic table of elements, is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties. The structure of the table shows periodic trends. The seven rows of the table, called periods, generally have metals on the left and non-metals on the right. The columns, called groups, contain elements with similar chemical behaviours. Six groups have accepted names as well as assigned numbers: for example, group 17 elements are the halogens; and group 18 are the noble gases. Also displayed are four simple rectangular areas or blocks associated with the filling of different atomic orbitals.

The organization of the periodic table can be used to derive relationships between the various element properties, and also to predict chemical properties and behaviours of undiscovered or newly synthesized elements. Russian chemist Dmitri Mendeleev published the first recognizable periodic table in 1869, developed mainly to illustrate periodic trends of the then-known elements. He also predicted some properties of unidentified elements that were expected to fill gaps within the table. Most of his forecasts proved to be correct. Mendeleev's idea has been slowly expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour. The modern periodic table now provides a useful framework for analyzing chemical reactions, and continues to be widely used in chemistry, nuclear physics and other sciences.

The elements from atomic numbers 1 (hydrogen) through 118 (oganesson) have been discovered or synthesized, completing seven full rows of the periodic table. The first 94 elements all occur naturally, though some are found only in trace amounts and a few were discovered in nature only after having first been synthesized. Elements 95 to 118 have only been synthesized in laboratories or nuclear reactors. The synthesis of elements having higher atomic numbers is currently being pursued: these elements would begin an eighth row, and theoretical work has been done to suggest possible candidates for this extension. Numerous synthetic radionuclides of naturally occurring elements have also been produced in laboratories.

Periodic table forms
Sets of elements
Elements
History
See also

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