p-block
 | This article needs additional citations for verification. (June 2012) |
Template:Periodic table (p-block)
The p-block of the periodic table of the elements consists of the last six groups except helium (which is located in the s-block). In the elemental form of the p-block elements, the highest energy electron occupies a p-orbital. The p-block contains all of the nonmetals (except for hydrogen and helium, which are in the s-block) and semimetals, as well as the poor metals.[not verified in body]
The groups of the p-block are:[not verified in body]
- 13 (IIIB, IIIA): Boron group
- 14 (IVB, IVA): Carbon group
- 15 (VB, VA): Nitrogen group (or pnictogens)
- 16 (VIB, VIA): Chalcogens
- 17 (VIIB, VIIA): Halogens
- 18 (0, VIIIA): Noble gases (excluding helium)
History
Many of the p-block elements have been known since antiquity, and all naturally occurring p-block elements with the exception of astatine were discovered[by whom?] before 1900.[1] Astatine was finally discovered in 1940 by Dale R. Corson, Kenneth Ross MacKenzie, and Emilio Segrè at the University of California, Berkeley.
The remaining p-block elements are hypothesized, based on periodic trends, to be elements 113–118, although it is currently unknown if they are actually p-block elements.[citation needed]
Properties
The p-block is one of two blocks in the periodic table to contain nonmetals (although the s-block only contains one nonmetal, hydrogen). As such, it has some of the most diverse properties of any region in the periodic table. The metals in this region of the periodic table are, in general, softer and have lower melting points than transition metals. The p-block is the only region of the periodic table to contain metalloids. In general, the farther one goes to the right, and the farther one goes up in the p-block, the less metallic the elements get; the metalloids form a diagonal line from the upper left to the lower right of the p-block.
All elements in the p-block have their outermost electron in a p-subshell.[citation needed]
Template:Periodic table (p-block trend)
References
- ^ "International Union of Pure and Applied Chemistry > Periodic Table of the Elements". Old.iupac.org. Retrieved 2012-08-13.
Concept Review with Key Terms 21.1 Properties and Trends in Group 3A—The elements of group 3A exhibit a range of physical and chemical properties. Many of the trends observed in this group can be understood from considerations of their electron configurations and their respective positions in the periodic table. For example, the inert pair of valence-shell electrons retained in the TI+ ion is also found in several other cations following a transition series.
21.2 Boron—Because they have only three valence electrons, boron atoms tend to form electron-deficient compounds, leading to some unusual bonding patterns. Compounds resulting from the “addition” of one structure to another, called adducts, are common when boron is present. Also, boron atoms form three-center bonds in the boron–hydrogen compounds called boranes. Other common boron compounds include borax, boric oxide, boric acid, and borates.
21.3 Aluminum—Aluminum is the most important element of group 3A. It is an active metal that is protected against corrosion by a film of Al2O3(s). Both Al2O3(s) and Al react with acids and strong bases. The production of aluminum is based on the amphoterism of Al2O3(s) and the electrolysis of Al2O3 in molten cryolite. The electron deficiency of aluminum chloride is a useful property in organic syntheses.
21.4 Carbon—Carbon is the key element of organic chemistry, but the free element also has uses. Diamond is prized for hardness and thermal conductivity; while graphite's electrical conductivity and refractory properties have found extensive use. Metal carbides, carbon oxides, and nitrogen-containing carbon compounds are of importance in a wide number of applications.
21.5 Silicon—Silicon is the key element of the mineral world, occurring as silica, SiO2 and as various minerals based on the silicate anion, SiO44−. Silica and silicates are common constituents of ceramics—solids that are characterized by hardness and brittleness and are chemically and structurally stable at high temperatures. Some synthetic silicon-containing organic compounds are of commercial importance, including the silicon-containing polymers called silicones.
21.6 Tin and Lead—Tin and lead metals are slightly more active than hydrogen and are widely used in alloys. They can have an oxidation number of either +2 or +4, with Sn(II) being a good reducing agent and Pb(IV) being a good oxidizing agent.
21.7 Nitrogen—Nitrogen is the major constituent of the atmosphere, and essentially all nitrogen compounds—natural and synthetic—are derived from the atmosphere. Some industrially important nitrogen compounds are ammonia, urea, nitric acid, ammonium salts, hydrazine, hydrazoic acid, and azides.
21.8 Phosphorus—The structure of phosphorus is based on the pyramidal molecule, P4, in both the white and red modifications. The structures of the oxides P4O6 and 4O10 are related to that of the P4 molecule. The principal compounds of phosphorus are the phosphates and polyphosphates.
21.9 Oxygen—Oxygen forms compounds with all elements except the lighter noble gases. Most oxygen is obtained, together with nitrogen and argon, by the fractional distillation of liquid air. Oxygen forms three types of anions when combined with active metals: oxide (O2−), peroxide (O22−) and superoxide (O2−) Ozone, O3, an allotrope of oxygen, is useful as an oxidizing agent, both in the laboratory and in the chemical industry.
21.10 Sulfur—Sulfur differs from oxygen in important ways, such as in its variety of allotropic forms and the changes they undergo. Its important compounds are the oxides, oxoacids, sulfites, sulfates, and thiosulfates, and many of the reactions of these compounds are oxidation–reduction reactions.
21.11 Selenium, Tellurium, and Polonium—Selenium and tellurium are found as minor but important components of technologies ranging from the coloring of glass to the detection of light. Polonium is highly radioactive and has few common uses.
21.12 Sources and Uses of the Halogens—The halogens (group 7A) are nonmetals; fluorine is the most nonmetallic of all elements. Fluorine and chlorine are prepared by electrolysis, and bromine and iodine by displacement reactions. Two halogens can react to form an interhalogen compound. Halogen atoms can substitute for H atoms in hydrocarbons and other organic compounds.
21.13 Hydrogen Halides—Hydrogen halides form by the direct combination of the elements or by the reaction of a halide salt with a nonvolatile acid. In aqueous solution, the hydrogen halides act as acids.
21.14 Oxoacids and Oxoanions of the Halogens—Important classes of halogen compounds include the oxoacids and their salts. The chemical reactions of these compounds are mostly oxidation–reduction reactions.
21.15 Occurrence of the Noble Gases—Most of the noble gases are found in Earth's atmosphere. Some, like He and Ar, are produced in quantity through the decay of radioactive isotopes of other elements. Radon is radioactive.
21.16 Properties and Uses of the Noble Gases—Interest in the noble gases centers on their physical properties and inertness. In contrast, the ability of the heavier noble gases to form some chemical compounds provides important insights into bonding theory.
