Halogens and Noble Gases

The halogens are all poisonous nonmetals, but they are so reactive that they are rarely found alone in nature. Why do they pair up with other elements so easily and often The clue, once again, is in their periodic table position. As Group 17 elements, their valence electron shell has seven electrons—only one electron away from being a full or complete shell. Many elements have an electron they can spare or at least share to fill a halogens outer shell. Halogens have 

Mendeleyev did not know about the noble gases when he wrote down his first periodic table. The noble gases were hidden from 

The halogens and noble gases, along with the BCNOs in Groups 13 through 16 are part of the periodic tables p block. The p block is named after the fact that the valence electrons in these elements come from the p orbital. 

Chlorine is probably familiar to most people as part of household bleach or the chemical used to keep swimming pools clean. Chlorine compounds are used to kill germs, manufacture 

Iodine is a germ-killer like chlorine and is also necessary for the health of the thyroid gland in humans. In fact, people who live close to nuclear power plants are often given emergency supplies of potassium iodine pills, in case the power plant has a leak of radioactive iodine. The pills flood the thyroid with normal iodine to keep the gland from absorbing the more harmful radioactive version of the element. 

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In contrast, the halogens and noble gases on the right of this block are distinctly nonmetallic. The noble gases, Group 18 of the periodic table, are monatomic gases that resist chemical attack because their electron configurations contain completely filled s and p orbitals. 

Krebs, Robert E. The history and use of our earth s chemical elements a reference guide. Westport (CT) Greenwood P, 1998. ix, 346p. ISBN 0-313-30123-9 A short history of chemistry — Atomic structure The periodic table of the chemical elements — Alkali metals and alkali earth metals - Transition elements metals to nonmetals — Metallics and metalloids - Metalloids and nonmetals — Halogens and noble gases - Lanthanide series (rare-earth elements) — Actinide, transuranic, and transactinide series... 

It is generally assumed that the properties of the various families of the periodic chart change smoothly from less metallic (or more electronegative) at the top of the family to more metallic (or less electronegative) at the bottom of the family. Certainly for the extremes of the chart—the alkali metals on the left and the halogens and noble gases on the right—this Is true the ionization potentials, for example, vary in a rather monotonous way. This is not true For certain central parts of the chart, however. 

Atomic absorption is used for the determination of ppm levels of metals. It is not normally used for the analysis of the light elements such as H, C, N, 0, P and S, halogens, and noble gases. Higher concentrations can be determined by prior dilution of the sample. AA is not recommended if a large number of elements are to be measured in a single sample. 

Sketch a plan of the periodic table, and fill in from memory the symbols of the first eighteen elements and the remaining alkali metals, halogens, and noble gases. 

Given a periodic table, identify the alkali metals, alkaline earth metals, halogens, and noble gases. (Section 2.3)... 

A FIGURE 11.5 Boiing pointsof the halogens and noble gases. This plot shows how the boiling points increase as the molecular weight increases due to stronger dispersion forces. 

Hazards to the public are dominated by the potential for release of radioactive volatile halogens and noble gases. These hazards have the highest consequences. 

Turner were used, representing every group in the periodic table with the exception of halogens and noble gases. 

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