Uncombined state

Copper occurs in the uncombined state in nature and is relatively easily obtained by the reduction of its compounds. It is not very active chemically and oxidises only very slowly in air at ordinary temperatures. 

Sodium (fifth most abundant element) is found principally as Na+ ion in water soluble salt deposits, such as NaCl, and in salt waters. The element reacts rapidly with water and with atmospheric oxygen, hence is not found in an uncombined state in nature. 

This element occurs in nature in the uncombined state as native copper and in the combined state as various oxides, sulfides, and carbonates. The chief mineral is chalcopyrite, CuFeS2, from which the element is extracted by roasting (heating in air) followed by reduction. The roasting reaction can be written... 

Hydrogen in its chemically uncombined state, however, is very rare on this planet. It almost never occurs in nature, and nearly all of it that we have is that which was obtained from its com-... 

A radical which can exist in the free or uncombined state. Such radicals are extremely reactive with themselves and with other neighbouring molecules. Free radicals are considered to take part in many reactions of importance to the rubber industry - vulcanisation, oxidation, ageing, polymerisation, etc. 

The oxidation numbers of Cl and Br in (a) have changed. Cl has changed from 0 to -1, while Br has changed from -1 to 0. (In diatomic molecules, the elements are considered to be in the uncombined state thus rule 1 applies.) There is no change in any oxidation number of any element in (b). Thus, (a)... 

An active electrode consists of an element (M) in its uncombined state which is capable of establishing an equilibrium with a solution that contains its ions ... 

Hydrogen occurs in small quantities in Nature in the uncombined state. It is found in a state of condensation in many rocks and in some specimens of meteoric iron. It is present in the gaseous discharges from oil and gas wells and volcanoes, and is also a constituent to a very minute extent of the atmosphere... 

Hydrogen in the uncombined state exists in enormous masses upon the sun, and is present in the "prominences observed in solar eclipses, while by optical means it may also be detected in many stars and nebulae. 

Early human civilizations used stone, bone, and wood for objects. Approximately ten thousand years ago, metals first appeared. The first metals used were those found in their native form, or in a pure, uncombined state. Most metals today are acquired from an ore containing the metal in combination with other elements such as oxygen. The existence of native metals is rare, and only a few metals exist in native form. Iron and nickel were available in limited supply from meteorites. The first metals utilized widely by humans were copper, silver, and gold. Pure nuggets of these metals were pounded, in a process known as cold hammering, with stones into various shapes used for weapons, jewelry, art, and various domestic implements. Eventually, smiths discovered if a metal was heated it could be shaped more easily. The heating process is known as annealing. Because the supply of native metals was limited, metal items symbolized wealth and status for those who possessed them. 

The oxidation number of an atom in its elementary uncombined state is 0. 

All the elements of the halogen family except astatine occur in nature in the form of their compounds. Because of their marked chemical activity, they are never found in nature in the uncombined state. 

The standard enthalpies of formation for all elements in uncombined state are arbitrarily taken as zero. 

In the elementary or uncombined state, the atoms are assigned an oxidation number of zero. 

When ammonium hydroxide dissociates electrolytically it yields the ion NHV". The group of atoms NH4, which is often spoken of as the ammonium radical, resembles in many respects the atom of sodium or potassium. Like these, it can form a monovalent positive ion, or it can form compounds with acid radicals, for example, NH4CI, (NID2SO4 but unlike sodium and potassium, it cannot exist in the uncombined state. 

Step 4 Next, balance any hydrogen or oxygen atoms that occur in a combined and uncombined state. For example, combined oxygen might be in the form of C02, while uncombined oxygen occurs as 02. 

Step 5 Finally, balance any other element that occurs in its uncombined state for example, Na or Cl2. 

Atmophile elements, tending to occur in the uncombined state (e.g., N, Ar) ... 

Noble metal— A metal that does not readily react with other elements and that, therefore, normally occurs in nature in a free, or uncombined, state. 

Copper was one of the earliest elements known to humans. At one time, it could be found lying on the ground in its native, or uncombined, state. Copper s distinctive red color made it easy to identify. Early humans used copper for many purposes, including jewelry, tools, and weapons. 

A is correct. Don t forget, the oxidation states for Cl and Br in and Br2 are zero by definition because the two elements are in their uncombined states. Chlorine gains electrons, so it is reduced. Since it is reduced, it is the oxidizing agent. Bromine loses electrons, so it is oxidized. 

For this type of combination reaction, each element goes from an uncombined state, where its oxidation state is zero, to a combined state in a compound, where its oxidation state is not zero. Thus reactions of this type are oxidation-reduction reactions (see Section 4-5). 

In free elements (that is, in the uncombined state), each atom has an oxidation number of zero. Thus each atom in H2, Br2, Na, Be, K, O2, and P4 has the same oxidation number zero. 

Electrolytic reduction of the molten chloride Electrolytic reduction of anhydrous oxide (in molten cryolite) Reduction of the metal oxide with a more electropositive metal, or reduction with coke and carbon monoxide These metals occur in the free (uncombined) state or can be obtained by roasting their sulfides... 

Cyanide ions are used to extract gold and silver. Although these metals are usually found in the uncombined state in nature, in other metal ores they may be present in relatively small concentrations and are more difficult to extract. In a typical process, the crushed ore is treated with an aqueous cyanide solution in the presence of air to dissolve the gold by forming the soluble complex ion [Au(CN)2] ... 

Copper, a rare element (6.8 X 10 percent of Earth s crust by mass), is found in nature in the uncombined state as well as in ores such as chalcopyrite, CuEeS2 (Figure 22.6). The reddish-brown metal is obtained by roasting the ore to give CU2S and then metallic copper ... 

Nitrogen is the most abundant terrestrial element in an uncombined state, as it makes up 78 percent of Earth s atmosphere as N2, but it is a minor component (19 parts per million) of Earth s crust. Nitrogen exists as two isotopes N (99.63% relative abundance) and N (0.4% abundance). Both isotopes are nuclear magnetic resonance (NMR) active, with the rarer N isotope being utilized more commonly in NMR spectroscopy because of its nuclear spin of one-half... 

Gold, silver, and platinum are members of a class of metals called noble metals because they are relatively unreactive. (The term noble implies a class set apart.) Other elements that appear in nature in the uncombined state are the elements in Group 8 helium, neon, argon, krypton, xenon, and radon. 

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