Magnesium oxide, oxidation state elements

Magnesium (eighth most abundant element) is found principally as Mg+2 ion in salt deposits, particularly as the slightly soluble carbonate, MgC03, and also in sea water. The element is oxidized by atmospheric oxygen and is not found in an uncombined state in nature. 

Although zinc is formally a 4-block element, some of its chemical properties are similar to those of the alkaline earth metals, especially those of magnesium. This is mainly due to zinc s exclusive exhibition of the +2 oxidation state in all its compounds and its appreciable electropositive character. With a standard potential of —0.763 V, zinc is considerably more electropositive than copper and cadmium. 

The most common simple cations in the soil solution are calcium (Ca2+), magnesium (Mg2+), potassium (K+), and sodium (Na+). Other alkali and alkaline-earth elements, when present, will be as simple cations also. Iron, aluminum, copper, zinc, cobalt, manganese, and nickel are also common in soil. Iron is present in both the ferrous (Fe2+) and ferric (Fe3+) states, while aluminum will be present as Al3+. Copper, zinc, cobalt, and nickel can all be present in one or both of their oxidations states simultaneously. Manganese presents a completely different situation in that it can exist in several oxidation states simultaneously. 

Beryllium fluoride (BeFj) is an example of beryllium that has an oxidation state of +2, combining with a negative anion element with an oxidation state of—1. BeryUiiun fluoride is also used along with magnesium metal in the chemical reduction process to produce beryllium metal. 

Indicate the position of beryllium, magnesium, calcium, strontium, and barium in Mendeleev s periodic table of the elements, the electron configurations and size of their atoms, and their oxidation states. 

Both magnesium metal and hydrogen gas are free elements and so have an oxidation state of 0. In sulfuric acid, hydrogen has an oxidation state of+1 since the overall charge on the sulfate ion is -2. Similarly, the oxidation state of magnesium in magnesium sulfate is +2. 

The mechanism of action for aluminum toxicity is not known, but the element is known to compete in biological systems with cations, especially magnesium (MacDonald and Martin 1988) despite an oxidation state difference, and to bind to transferrin and citrate in the blood stream (Gannot 1986). It may also affect second messenger systems and calcium availability (Birchall and Chappell 1988), and irreversibly bind to cell nucleus components (Crapper-McLachlan 1989 Dryssen et al. 1987). Aluminum has also been shown to inhibit neuronal microtubule formation. However, much more work is needed before a mechanism can be proposed. 

Reactive electrodes refer mostly to metals from the alkaline (e.g., lithium, sodium) and the alkaline earth (e.g., calcium, magnesium) groups. These metals may react spontaneously with most of the nonaqueous polar solvents, salt anions containing elements in a high oxidation state (e.g., C104 , AsF6 , PF6 , SO CF ) and atmospheric components (02, C02, H20, N2). Note that ah the polar solvents have groups that may contain C—O, C—S, C—N, C—Cl, C—F, S—O, S—Cl, etc. These bonds can be attacked by active metals to form ionic species, and thus the electrode-solution reactions may produce reduction products that are more stable thermodynamically than the mother solution components. Consequently, active metals in nonaqueous systems are always covered by surface films [46], When introduced to the solutions, active metals are usually already covered by native films (formed by reactions with atmospheric species), and then these initial layers are substituted by surface species formed by the reduction of solution components [47], In most of these cases, the open circuit potentials of these metals reflect the potential of the M/MX/MZ+ half-cell, where MX refers to the metal salts/oxide/hydroxide/carbonates which comprise the surface films. The potential of this half-cell may be close to that of the M/Mz+ couple [48],... 

In this equation, the free elements have oxidation states of zero and the oxidation states have been assigned to Mg and Cl in magnesium chloride. Next, separate the two elements that have undergone a change in oxidation state ... 

Mendeleev was convinced that he had discovered what he called the Periodic Law. The principle of the law was that the characteristics of the elements would vary periodically (that is, repeat at set intervals) as atomic weight went up. Characteristics such as specific density, oxidation states, and affinity (degree of chemical interactions) would vary for each element, but such variation was within a specific range that was common to a particular group. Thus, calcium (element 20) might be much heavier than magnesium (element 12) and only a bit heavier than potassium (element 19), but calcium and magnesium were related by chemical behavior. 

E3.37 As noted in Section 3.17(a), nonstochiometry is common in the solid-state compounds of d-, f-, and later p-block elements. We would therefore expect vanadium carbide and manganese oxide to exhibit nonstoichiometry (two d-block metal compounds) but not magnesium oxide (an s-b ock metal oxide). 

One sees that the oxidation state equals the charge of the ion. The cations are normally named just by adding ion after the name of the element (Mg = magnesium ion) whereas the suffix -id replaces the suffix of the element for anions (Cf = chloride). For composite ions, a shared (total) oxidation number is used. This shared oxidation state is the sum of all the oxidation states for the different ions in the composite ion. Uncharged atoms have the oxidation number of zero. The ammonium ion and hydroxide are both examples of composite ions ... 

The types of substance that are thermoluminescent, either in their natural state or after radiation bombardment, include (112) the alkali metal halides, calcite, dolomite, fluorite, aluminum oxide, magnesium oxide, gypsum, quartz, glass, feldspars, feldspathoids, certain dried clays, and ceramic materials. Of over 3000 rock samples examined for thermoluminescence, some 75% showed visible fight emission (112). Nearly all limestones and acid igneous rocks are naturally thermoluminescent, due mainly to the presence of trace elements of uranium, thorium, and so on. Calcium and magnesium... 

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