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When rhombic sulfur melts, the straw-colored liquid is quite mobile; its viscosity is low because S 8 molecules are essentially spherical and offer relatively little resistance as they move past each other. As the temperature rises, S-S bonds in the rings break, and polymeric chains of sulfur atoms result. These chains combine end to end, forming still longer chains that tangle with one another. The liquid gradually darkens in color and becomes so viscous that finally (at about 230 °C) it does not pour easily. The dangling atoms at the ends of the chains of sulfur atoms are responsible for the dark red color because their electronic structure differs from those of sulfur atoms that have bonds to two adjacent sulfur atoms. This causes them to absorb light differently and results in a different visible color. Cooling the liquid rapidly produces a rubberlike amorphous mass, called plastic sulfur.

Sulfur boils at 445 °C and forms a vapor consisting of S 2 , S 6 , and S 8 molecules; at about 1000 °C, the vapor density corresponds to the formula S 2 , which is a paramagnetic molecule like O 2 with a similar electronic structure and a weak sulfur-sulfur double bond.

As seen in this discussion, an important feature of the structural behavior of the nonmetals is that the elements usually occur with eight electrons in their valence shells. If necessary, the elements form enough covalent bonds to supplement the electrons already present to possess an octet. For example, members of group 15 have five valence electrons and require only three additional electrons to fill their valence shells. These elements form three covalent bonds in their free state: triple bonds in the N 2 molecule or single bonds to three different atoms in arsenic and phosphorus. The elements of group 16 require only two additional electrons. Oxygen forms a double bond in the O 2 molecule, and sulfur, selenium, and tellurium form two single bonds in various rings and chains. The halogens form diatomic molecules in which each atom is involved in only one bond. This provides the electron required necessary to complete the octet on the halogen atom. The noble gases do not form covalent bonds to other noble gas atoms because they already have a filled outer shell.

Key concepts and summary

Nonmetals have structures that are very different from those of the metals, primarily because they have greater electronegativity and electrons that are more tightly bound to individual atoms. Most nonmetal oxides are acid anhydrides, meaning that they react with water to form acidic solutions. Molecular structures are common for most of the nonmetals, and several have multiple allotropes with varying physical properties.

Chemistry end of chapter exercises

Carbon forms a number of allotropes, two of which are graphite and diamond. Silicon has a diamond structure. Why is there no allotrope of silicon with a graphite structure?

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Nitrogen in the atmosphere exists as very stable diatomic molecules. Why does phosphorus form less stable P 4 molecules instead of P 2 molecules?

In the N 2 molecule, the nitrogen atoms have an σ bond and two π bonds holding the two atoms together. The presence of three strong bonds makes N 2 a very stable molecule. Phosphorus is a third-period element, and as such, does not form π bonds efficiently; therefore, it must fulfill its bonding requirement by forming three σ bonds.

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Write balanced chemical equations for the reaction of the following acid anhydrides with water:

(a) SO 3

(b) N 2 O 3

(c) Cl 2 O 7

(d) P 4 O 10

(e) NO 2

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Determine the oxidation number of each element in each of the following compounds:

(a) HCN

(b) OF 2

(c) AsCl 3

(a) H = 1+, C = 2+, and N = 3−; (b) O = 2+ and F = 1−; (c) As = 3+ and Cl = 1−

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Determine the oxidation state of sulfur in each of the following:

(a) SO 3

(b) SO 2

(c) SO 3 2−

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Arrange the following in order of increasing electronegativity: F; Cl; O; and S.


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Why does white phosphorus consist of tetrahedral P 4 molecules while nitrogen consists of diatomic N 2 molecules?

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Questions & Answers

hello everyone... please how can I calculate and explain electronegativity?
Meek Reply
hello everyone... please how can I explain electronegativity?
Tendency to pull electrons
explain why the atomic size of fluorine atom is smaller than that of Be
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copper is purified by electrolysis.it transfers copper atom from an impure copper anode to a pure copper cathode,leaving the impurities behind.
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period 2
the volume of nitrogen is 6L at 35degrees celsius and 740 torr l.what is the volume will it occupy at S.T.P?
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Use, PV=nRT with correct units to obtain volume.
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Graham's law of diffusion states that the rate of diffusion of a gas is inversely proportional to the square root of it's molecular weight
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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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