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The name phosphorus comes from the Greek words meaning light bringing. When phosphorus was first isolated, scientists noted that it glowed in the dark and burned when exposed to air. Phosphorus is the only member of its group that does not occur in the uncombined state in nature; it exists in many allotropic forms. We will consider two of those forms: white phosphorus and red phosphorus.

White phosphorus is a white, waxy solid that melts at 44.2 °C and boils at 280 °C. It is insoluble in water (in which it is stored—see [link] ), is very soluble in carbon disulfide, and bursts into flame in air. As a solid, as a liquid, as a gas, and in solution, white phosphorus exists as P 4 molecules with four phosphorus atoms at the corners of a regular tetrahedron, as illustrated in [link] . Each phosphorus atom covalently bonds to the other three atoms in the molecule by single covalent bonds. White phosphorus is the most reactive allotrope and is very toxic.

Two photos and two diagrams are shown and labeled “a,” “b,” “c,” and “d.” Photo a shows a test tube that contains a solid yellow compound. Diagram b shows a four-sided pyramid shape that has an atom at each corner. Photo c shows a dark black powder in a watch glass. Diagram d shows two four-sided pyramid shapes that have an atom at each corner and are connected together by a single bond.
(a) Because white phosphorus bursts into flame in air, it is stored in water. (b) The structure of white phosphorus consists of P 4 molecules arranged in a tetrahedron. (c) Red phosphorus is much less reactive than is white phosphorus. (d) The structure of red phosphorus consists of networks of P 4 tetrahedra joined by P-P single bonds. (credit a: modification of work from http://images-of-elements.com/phosphorus.php)

Heating white phosphorus to 270–300 °C in the absence of air yields red phosphorus. Red phosphorus (shown in [link] ) is denser, has a higher melting point (~600 °C), is much less reactive, is essentially nontoxic, and is easier and safer to handle than is white phosphorus. Its structure is highly polymeric and appears to contain three-dimensional networks of P 4 tetrahedra joined by P-P single bonds. Red phosphorus is insoluble in solvents that dissolve white phosphorus. When red phosphorus is heated, P 4 molecules sublime from the solid.


The allotropy of sulfur is far greater and more complex than that of any other element. Sulfur is the brimstone referred to in the Bible and other places, and references to sulfur occur throughout recorded history—right up to the relatively recent discovery that it is a component of the atmospheres of Venus and of Io, a moon of Jupiter. The most common and most stable allotrope of sulfur is yellow, rhombic sulfur, so named because of the shape of its crystals. Rhombic sulfur is the form to which all other allotropes revert at room temperature. Crystals of rhombic sulfur melt at 113 °C. Cooling this liquid gives long needles of monoclinic sulfur. This form is stable from 96 °C to the melting point, 119 °C. At room temperature, it gradually reverts to the rhombic form.

Both rhombic sulfur and monoclinic sulfur contain S 8 molecules in which atoms form eight-membered, puckered rings that resemble crowns, as illustrated in [link] . Each sulfur atom is bonded to each of its two neighbors in the ring by covalent S-S single bonds.

Four diagrams are shown and labeled “a,” “b,” “c,” and “d.” Diagram a shows four ring structures that are each made up of eight single bonded atoms. Diagram b shows four chains of eight atoms. Diagram c shows three chains of atoms, one composed by nine atoms, one by twelve atoms and one by eleven atoms. Diagram d shows the same three chains, but this time they are much closer together and slightly intertwined.
These four sulfur allotropes show eight-membered, puckered rings. Each sulfur atom bonds to each of its two neighbors in the ring by covalent S-S single bonds. Here are (a) individual S 8 rings, (b) S 8 chains formed when the rings open, (c) longer chains formed by adding sulfur atoms to S 8 chains, and (d) part of the very long sulfur chains formed at higher temperatures.

Questions & Answers

what is hydrocarbon
Sensible Reply
this is an organic compound that consist of hydrogen and ox
why is isotonic solution the as blood
Hawa Reply
Elaborate more pls
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what is hydrocarbon? pls
Hydrocarbon are organic compound consisting of hydrogen and carbon atoms
why is electrolytes really active in water
relationship between an orbit and a shell
Hawa Reply
relationship between orbit and a shell
What a homogenous mixture
Allison Reply
Define homologous series
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it is an organic compound having the same chemical properties which differs in a successive member of CH4
when iron is exposed to moisture and it rusts,the value of deltaG for the reaction is
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what is chemistry
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it is a branch of science that deals with the mixture of chemicals and properties and uses of matter
define aci according to Lewis
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an acid is an electron pair acceptor according to lewis
What is a homogenous mixture
the third ionization energy of aluminium
sanmi Reply
name the allotrope of carbon used in gas masks
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Discuss the synthesis of sucrose
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What is a glycoside and discuss the formation
explain the transitioning of glucose molecules from Fischer projection of glucose to the Haworth projection
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what is quantum
hezekiah Reply
what are metalliod
Metalloids are substances having the characteristics of both metals and non-metals
what is acid
define acid according to lewis
Acid is an electron acceptor
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what is valency
odukoya Reply
The number of chemical bonds the atoms of a certain element can form.
what is ionization energy?
Hussniz Reply
ionization energy is qualitatively defined as the minimum amount of energy required to remove the most loosely bound electron, the valence electron, of an isolated neutral gaseous atom, molecule or io
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Very explanatory. Tanx
Practice Key Terms 2

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Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
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