Calcium atoms, reactions

A more classical cleavage of an inseparable mixture of 1-cyclopentadienyl-and l-chloro-2,5-bis(trimethylsilyl)-3,4-dimethylphospholes with distilled calcium gave a complex structure 12 containing four calcium atoms. Reaction of calcium with the corresponding pure chloroarsole gave the dicalcium dimer 12a (Scheme 4) [26]. 

As evidenced by the tremendous power of nuclear bombs, nuclear reactions involve quite a lot of energy. In the laboratory, researchers fabricate nuclides with the aid of special, high-energy equipment such as reactors in which nuclear reactions can take place, or particle accelerators in which particles such as protons are accelerated to high speed and crash into one another, or some other target. For example, in 2006, researchers at the Joint Institute for Nuclear Research in the Russian Federation and the Lawrence Livermore National Laboratory in California synthesized isotopes of element 118 for the first time. To make the new isotope, researchers smashed calcium atoms into a target made of californium (which has an atomic number of 98). These new isotopes decayed quickly. (Element 118 and other recently discovered elements have not yet been named.)... 

In the first reaction, a single calcium atom donates two electrons to two chlorine atoms. This results in the formation of a Ca + ion and two Cl ions. The positive ion and two negative ions are attracted to each other. In the formation of magnesium oxide, magnesium donates two electrons to oxygen resulting in Mg and... 

Klabunde et al. (66) reported that calcium atoms react with unsaturated perfluoroorganic compounds, but there is no reaction with perfluo-roalkanes. Organocalcium compounds were not isolated, but their presence was inferred from reactions of the condensates at low temperatures. The final products on warming to room temperature were calcium fluoride and defluorinated organic compounds, e.g.,... 

Reactions within a van der Waals (vdW) complex of calcium with hydrogen halides (HC1 and HBr) lead to electronically excited calcium halides. These reactions have been quite extensively studied in full collisions of excited calcium beams (Brinckmann et al. 1980 Brinckmann and Telle 1977 Rettner and Zare 1981, 1982 Telle and Brinckmann 1990). The electronic excitation of the calcium atom results in a strong chemiluminescence under collisional conditions. The efficiency of this chemiluminescence depends upon the electronic state and the fine structure component, and the final product state is influenced by the preparation conditions of the collision. In the reaction Ca(4s4p1P1) + HC1, the direction of the polarization of the P orbital with respect to the collision relative velocity (pK or pff) has an effect on the branching ratio to the products CaCl, A2n or B2X+ (Rettner and Zare 1981, 1982). 

Insertion reactions of calcium atoms into M14—M14 bonds yield symmetrical or unsym-metrical M14—Ca compounds according to Scheme 144 and equation 6989. A trimethylsi-lyl trimethylstannyl calcium was also characterized chemically in the cocondensation of calcium with trimethylsilyl trimethylstannane90. Calcium bis(stannide) (equation 69) crystallizes in the form of colorless cuboids in a centrosymmetric space group PI. The calcium atom lies on the crystallographic center of inversion in the middle of the linear Sn—Ca—Sn chain. The calcium atom is coordinated in a distorted octahedral fashion by two tin atoms... 

Thus, it was stated that the initial stages of mechanochemical reaction of Ca(OH)2 with HTD are connected with the transport of mobile protons from the acidic oxide to basic one, and with the change of electron density at the neighboring titanium and calcium atoms. These processes result in the formation of water molecules and Ca-O-Ti bonds. 

The non-aqueous oxidation of various ketones and aldehydes to hydroxyaldehydes and hydroxy ketones has been carried out in two steps the first step is a bromination and the second a hydrolysis, or replacement of the bromine atoms by hydroxyl groups. Fischer and Landsteiner " brominated acetal in the presence of calcium carbonate (reaction 20). The bromoaldehyde Avas then treated with cold barium hydroxide solution (reaction 21) the resulting glycolic aldehyde was identified by conversion to glyoxal phenylosazone (reaction 22) and by the formation of calcium glycolate, after oxidation with bromine (reaction 23). 

In an attempt to synthesize and capture silver clusters in this way, empty Ag, K-A was exposed to Cs(g) at 250 °C. The structure of the product showed that the potassium ions had all been reduced and were no longer present in the zeolite. The silver ions also had all been reduced to atoms, but most of these were found as hexasilver molecules at the very centers of the large cavities. Each hexasilver molecule was surroxmded by fourteen Cs" " cations. When this reaction was done with Ag, Ca-A and Rb(g) instead, hexasilver molecules each associated with thirteen Rb" " ions were found at the same position. The product calcium atoms had left the structure. 

The second column from the left contains the alkaline earth metals, beryllium, magnesium, calcium, strontium, barium, and radium (Be, Mg, Ca, Sr, Ba, and Ra, respectively). Magnesium and calcium are present everywhere and are needed by our salty bodies and the salty bodies of our fellow creatures. Calcium is vital to bones, teeth, seashells, and exoskeletons. Calcium plays a critical role in the operation of our muscles as well as communication between cells. Because strontium is in this family, radioactive strontium, a fission product of certain atomic reactions, can be absorbed by the body and used as it would use calcium. Radium, another radioactive element, is also found in this family. 

Calcium reacts with chlorine to form acom-pound called calcimn chloride, CaCl2, which is often used for deicing roads. In the reaction, each calcium atom loses two electrons while two chlorine atoms each gain one electron. Use the format shown in Table 4.2 to analyze this reaction. What role does the coefficient 2 play in the reaction ... 

Chemical reactions between two or more species from the analytical sample also can occur. The calcium-phosphorus system has been one of those most extensively studied. Calcium, in the presence of phosphate, produces a stable calcium-phosphorus compound that removes large numbers of calcium atoms from the flame. The result is a severe depression of the calcium absorption signal. The same effect is observed with strontium in the presence of phosphate. 

Chemical Interference. Incomplete atomization of the analyte causes chemical interference, due to the fact that atomic absorption can only occur with free atoms. Reactions in the flame which lead to the formation of thermally stable species decrease the signal. This is responsible for the depression of calcium signals in serum analysis by proteins, as well as for the low sensitivities of metals which form thermally stable oxides or carbides (Al, B, V, etc.) in flame AAS. A further example of chemical interference is the suppression of the extinction of alkaline earth metals as a result of the presence of oxyanions (OX) such as aluminates or phosphates. This well-known calcium phosphate interference is caused by the reaction ... 

The reaction of excited calcium atoms with HCl has been widely studied in beam gas experiments (i3-, and Rettner et al( ) have shown that the Ca P + HCl reaction is sensitive to the orientation of the calcium orbital with respect to the relative velocity in the collision. This reaction produces Ca Cl (A,B) with a high cross section 60... 

We have studied the Ca + HCl reaction as produced within a complex in the same way as for electronic relaxation. We form the Ca-HCl complex in the ground state and excite it close to a transition of the calcium atom. We therefore reach an excited surface which will lead to the reaction into CaCl (A,B) + H. This reaction is believed to proceed through a crossing of the attained covalent surface and the ionic Ca" " + HC1 one. Tuning with a laser across the absorption of the Ca HCl system allows us to explore the entrance valley of the reaction and part of the crossing seam, through the spectroscopic analysis of the spectra. 

We therefore think that the absorption inducing the reaction arises from the allowed Calcium transitions either directly through or by state mixing in the Calcium for D2 (It is known that D2 Calcium atoms absorb in rare gas matrixes(20)) However the transition is spin forbidden... 

From this, you see Ihat the Ca and O atoms change in oxidation number during the reaction. In effect, each calcium atom in the metal loses two electrons to form Ca ions, and each oxygen atom in O2 gains two electrons to form 0 ions. The net result is a transfer of electrons from calcium to oxygen, so this reaction is an oxidation-reduction reaction. In other words, an oxidation-reduction reaction (or redox reaction) is a reaction in which electrons are transferred between species or in which atoms change oxidation number. 

Note that calcium has gained in oxidation number from 0 to +2. (Each calcium atom loses two electrons.) We say that calcium has been oxidized. Oxygen, on the other hand, has decreased in oxidation number from 0 to —2. (Each oxygen atom gains two electrons.) We say that oxygen has been reduced. An oxidation-reduction reaction always involves both oxidation (the loss of electrons) and reduction (the gain of electrons). 

In this reaction, the calcium atom is oxidized, because it increases in oxidation number (from 0 to +2, as in the previons equation). Chlorine is reduced it decreases in oxidation number from 0 to 1. This is clearly an oxidation-reduction reaction that does not involve oxygen. 

In this reaction, each calcium atom loses two electrons (is oxidized) and each oxygen atom gains two electrons (is reduced). The corresponding half-reactions are... 

The element Ca in the reactants has a charge of 0, but in the CaS product, it is present as a ion. Because the charge is more positive, we know that the calcium atom lost two electrons, which means that calcium metal was oxidized in the reaction. 

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