solid, liquid, or gas, at standard temperature and pressure (STP). Most elements are solids at STP, while several are gases. Only bromine and mercury are A chemical element is a species of atom defined by its number of protons. The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8: each oxygen atom has 8 protons in its nucleus. Atoms of the same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Atoms of one element can be transformed into atom A… A commonly used basic distinction among the elements is their state of matter (phase), whether solid, liquid, or gas, at standard temperature and pressure (STP). Most elements are solids at STP, while several are gases. Only bromine and mercury are liquid at 0 degrees Celsius (32 degrees Fahrenheit) and 1 atmosphere pressure; caesium and gallium are solid at that temperature, but melt at 28.4 °C (83.1 °F) and 29.8 °C (85.6 °F), respectively. Melting and boiling points, typically expressed in degrees Celsius at a pressure of one atmosphere, are commonly used in characterizing the various elements. Those elements with boiling points above 2,000 C are termed refractory, while those easily vaporized are volatiles. The element with the widest range between melting and boiling points is gallium, which boils at 2,204 °C (3,999 °F). While known for most elements, either or both of these measurements is still undetermined for some of the radioactive elements available in only tiny quantities. Since helium remains a liquid even at absolute zero at atmospheric pressure, it has only a boiling point, and not a melting point, in conventional presentations. Under conditions of stable equilibrium, solid elements are structured into a crystalline form, with each element having its own structure. These belong to the seven families of crystal structures: cubic (including body-centered and face-centered), triclinic, hexagonal, monoclinic, orthorhombic, rhombohedral, and tetragonal. Over 30 elements crystallize in the cubic form. 40% of the elements form close-packed crystals: either face-centered cubic or hexagonal close-packed. For some of the synthetically produced transuranic elements, available samples have been too small to determine crystal structures. Under the high pressure conditions found within a planetary interior, elements can appear in new crystalline forms, forming allotropes. For example, seven dense classes of silicon crystals can appear at pressures from 1 MPa to 100 GPa, under room temperature conditions. In the extreme conditions found inside a carbon-rich white dwarf, diamond-like amorphous glass may form. The density at selected standard temperature and pressure (STP) is often used in characterizing the elements. The mass density of an element depends on the mass of the atomic nucleus and the separation between the atoms created by the bound electrons. Density is given in kilograms per cubic meter (kg/m3), but may also be expressed in grams per cubic centimetre (g/cm3). Since several elements are gases at commonly encountered temperatures, their densities are usually stated for their gaseous forms; when liquefied or solidified, the gaseous elements have densities similar to those of the other elements. The general trend is for densities to increase as the atomic number rises. Lower density elements are the noble gases and the alkali metals. Higher densities are found in the middle of the rows of the periodic elements, as they can form more covalent bonds, drawing the atoms closer together. The naming of various substances now known as elements precedes the atomic theory of matter, as names were given locally by various cultures to various minerals, metals, compounds, alloys, mixtures, and other materials, though at the time it was not known which chemicals were elements and which compounds. As they were identified as elements, the existing names for anciently known elements (e.g., gold, mercury, iron) were kept in most countries. National differences emerged over the element names either for convenience, linguistic niceties, or nationalism. For example, German speakers use "Wasserstoff" (water stuff) for "hydrogen", "Sauerstoff" (acid stuff) for "oxygen", and "Stickstoff" (smothering stuff) for "nitrogen"; English and some other languages use "sodium" for "natrium", and "potassium" for "kalium"; and the French, Italians, Greeks, Portuguese and Poles prefer "azote/azot/azoto" (from roots meaning "no life") for "nitrogen". In the past, the name for new elements was traditionally decided by their discoverers. This changed in 1947, when a conference of the International Union of Pure and Applied Chemistry (IUPAC) decided that the names and symbols of new elements would be determined by the IUPAC. The discoverer of a new element had the right to suggest a name, but for purposes of international communication and trade, the official names of the chemical elements both ancient and more recently recognised are decided by the IUPAC. The IUPAC organization has decided on a style of international English language as a Lingua franca, drawing on traditional English names even when an element's chemical symbol is based on a Latin or other traditional word. For example, adopting "gold" rather than "aurum" as the name for the 79th element (Au). IUPAC prefers the British spellings "aluminium" and "caesium" over the U.S. spellings "aluminum" and "cesium", and the U.S. "sulfur" over British "sulphur". However, elements that are practical to sell in bulk in many countries often still have locally used national names, and countries whose national language does not use the Latin alphabet are likely to use the IUPAC element names. New elements have been named for their properties, after a mineral from which it was extracted, the location of its discovery, a mythical subject, an astronomical object, or a prominent scientist. According to IUPAC, element

New thermodynamic regularity for cesium over the whole liquid range In this paper we derive an equation of state for liquid cesium based on a suggested potential function in accord to the characteristics large attraction and soft repulsion at the asymptotes of interaction potentials. By considering the interaction of nearest adjacent atoms in dense fluid, the equation of state predicts that the isotherm is linear function of, where is the compression factor, is the molar volume, and is the molar density. The linear parameters are identified as interaction coefficients related to attraction and repulsion, and are used to evaluate the molecular parameters with interesting implications. The isotherm is intended to resolve the particular thermodynamic properties of alkali metals, which have been known for their unusual change of the nature of intermolecular force as the characteristic metal-nonmetal transition range is approached. When applied to liquid cesium, the isotherms persist linear over the whole liquid range including the metal non-metals transition range and at the critical temperature perfectly. [physics/0503135] New thermodynamic regularity for cesium over the whole liquid range Skip to main content Search arXiv Press Enter to search · Advanced search --> Physics > Chemical Physics arXiv:physics/0503135 (physics) [Submitted on 16 Mar 2005] Title: New thermodynamic regularity for cesium over the whole liquid range Authors: M.H. Ghatee , M. Bahadori View a PDF of the paper titled New thermodynamic regularity for cesium over the whole liquid range, by M.H. Ghatee and M. Bahadori View PDF Abstract: In this paper we derive an equation of state for liquid cesium based on a suggested potential function in accord to the characteristics large attraction and soft repulsion at the asymptotes of interaction potentials. By considering the interaction of nearest adjacent atoms in dense fluid, the equation of state predicts that the isotherm is linear function of, where is the compression factor, is the molar volume, and is the molar density. The linear parameters are identified as interaction coefficients related to attraction and repulsion, and are used to evaluate the molecular parameters with interesting implications. The isotherm is intended to resolve the particular thermodynamic properties of alkali metals, which have been known for their unusual change of the nature of intermolecular force as the characteristic metal-nonmetal transition range is approached. When applied to liquid cesium, the isotherms persist linear over the whole liquid range including the metal non-metals transition range and at the critical temperature perfectly. The isotherm is equivalent to a virial (like) EOS for which the linear parameters of the isotherm form the corresponding second and third virial coefficients. Ghatee [ view email ] [v1] Wed, 16 Mar 2005 14:19:28 UTC (292 KB) Full-text links: Access Paper: View a PDF of the paper titled New thermodynamic regularity for cesium over the whole liquid range, by M.H. Ghatee and M. Bahadori View PDF view license Current browse context: physics.chem-ph < prev | next > new | recent | 2005-03 References & Citations NASA ADS Google Scholar Semantic Scholar export BibTeX citation Loading... BibTeX formatted citation × loading... Data provided by: Bookmark Bibliographic Tools Bibliographic and Citation Tools Bibliographic Explorer Toggle Bibliographic Explorer ( What is the Explorer?

Choice of type and placement of thrusters on spacecraft (s/c) should include consideration of their effects on other subsystems. Models are presented of the exhaust plumes of mercury, cesium, colloid, hydrazine, ammonia, and Teflon rockets. Effects arising from plume impingement on s/c surfaces, radio frequency interference, optical interference, and earth environmental contamination are discussed. Some constraints arise in the placement of mercury, cesium, and Teflon thrusters. Few problems exist with other thruster types, nor is earth contamination a problem.