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Alkaline earth metal atoms

Spectra of helium and the alkaline earth metal atoms... [Pg.219]

The rather complex structure of the compound NaZn13 was studied by Ketelaar (1937) and by Zintl and Haucke (1938). Every Na atoms is surrounded by 24 Zn atoms at the same distance. The lattice parameters of several MeZn13 compounds pertaining to this structural type are, in a first approximation, independent of the size of the alkali (or alkaline earth) metal atom. Similar consideration may be made for the MeCd13 compounds. Zintl, therefore, considered the fundamental component of this crystal structure to be a framework of Zn (or Cd) atoms with the alkali (or alkaline earth) metal atoms occupying the holes of the framework. However notice (Nevitt 1967) that in compounds MeX13 radius ratios (rMe/rx) deviating by more than about 15% from the mean value 1.54 are unfavourable for the occurrence of the structure. [Pg.728]

Symbol Mg atomic number 12 atomic weight 24.305 a Group II A (Group 2) alkaline-earth metal atomic radius 1.60A ionic radius (Mg2+) 0.72A atomic volume 14.0 cm /mol electron configuration [Ne]3s2 valence +2 ionization potential 7.646 and 15.035eV for Mg+ and Mg2+, respectively three natural isotopes Mg-24(78.99%), Mg-25(10.00%), Mg-26(11.01%). [Pg.510]

Relativistic effects in photoionization of atoms encaged in C60/ A Cso, have fallen under theoretical scrutiny in [29,30], where the photoionization spectra of valence ns subshells in encaged alkaline-earth-metal atoms ( Mg, Ca, Sr and Ba) were detailed. The corresponding key results of [29,30] are highlighted in this section. [Pg.61]

The oxidation number of any alkaline earth metal atom in any of its compounds is always equal to +2. [Pg.446]

A variant of the crossed-beam geometry, simpler but efficient in some cases, is the beam-gas arrangement. It leads usually to much larger signal than in the crossed-beam configurations, at the expense of a less accurate definition of the reaction kinematics. It is used fairly often to study the total cross-sections of chemiluminescent processes, especially when the species which is to be put into the beam is refractory, as are the transition metals [39, 40]. Reactions of alkaline earth metal atoms have been studied by this technique [41]. [Pg.3007]

The Double Harpoon a Mechanism Adapted to Alkaline Earth Metal Atom Reactions... [Pg.3013]

Alkaline earth metal atoms have fairly low ionization potentials, as have alkali metal atoms (e.g., 5.21 and 5.14 eV for barium and sodium, respectively [89]). Hence the reactions of alkaline earth metal atoms with oxidizing molecules are also expected to be initiated by an electron transfer and should follow the harpoon mechanism. However, alkali metal atoms are monovalent species, whereas alkaline earth metal atoms have two valence electrons. Hence peculiarities are to be expected in the alkaline earth metal reaction dynamics, especially when doubly charged products such as BaO are to be formed [90]. The second valence electron also opens up the possibility of chemiluminescent reactions, which are largely absent in alkali metal atom reactions [91, 92]. The second electron causes the existence of low-lying excited states in the product. [Pg.3013]

Reactions of ground-state alkaline earth metal atoms have been the subject of too... [Pg.3013]

Since alkaline earth metal atoms have two valence electrons, it is convenient to distinguish between reaction products, which have a single ionic bond such as BaCl (Ba+Cr) from products having a double ionic bond in the ground state such as BaO (BaO has the structure Ba +O in the ground state and Ba+O in the lowest excited states). [Pg.3014]

The reactions of alkaline earth metal atoms with halogen molecules, either forming alkaline earth metal monohalides or leading to chemi-ionization, represent an important case study in the reaction dynamics of divalent systems [91, 92, 95-100]. Let us take as an example the reaction... [Pg.3014]

The gas-phase chemistry of ground-state transition metals is much less well understood and has attracted far fewer studies than the reaction dynamics of alkali and alkaline earth metal atoms. Three reasons explain this situation. The first is expert-... [Pg.3018]

Dramatic effects of electronic excitation on the reaction mechanisms have been demonstrated in several cases. One of the first reported examples must be recalled here also as it falls outside the scope of this chapter. Electronically excited 0( D) is much more reactive than ground-state 0( P) and inserts into the C-H bonds of methane [162]. Similar state specificity in the reactivity has also been encountered in electron-transfer reactions and seems to be the rule in light systems. Its origin has been explored systematically in alkali and alkaline earth metal atom reactions. Before discussing some of the studies, it is appropriate to survey a much simpler situation where electronic excitation affects the dynamics of the reaction just by changing the location of the electron-transfer region. [Pg.3025]

Measuring the polarization of the reaction product is also an important issue in stereodynamics. A lot of the activity in this field concerns the reactivity of alkaline earth metal atoms since the corresponding reaction products are easy to probe by optical techniques. A full account of methods to measure product alignment and orientation in bimolecular collisions has been given by Orr-Ewing and Zare [18]. Such measurements, with the help of simple models such as the DIPR-DIP model considered Section 2.3.2, give insight into the shape of the reactive system at the moment where forces are released [86, 87, 184, 195, 233, 234]. [Pg.3032]

Alkaline earth metal atoms also are capable of such reactions. ... [Pg.546]

In Figure 2, the ELF curves for some selected atoms are depicted. Here, one can use the spherical symmetry to plot it as a function of only one variable, the distance to the nuclei. It is interesting to note that for the alkaline metal atoms the ELF does not decay to zero when the distance goes to infinity. The same fact occurs for the alkaline-earth-metal atoms and for any spherical system with an outer shell formed only by electrons on s-orbitals. In fact, for the hydrogen atom, the ELF is equal to one everywhere. On the other side, one can perfectly see the shell structure even for mbidium atom. The same is true for the noble gas atoms and, as shown by Kohout and Savin,22 for all the atoms to Sr. [Pg.64]

The deposition of alkaline-earth-metal atoms and ozone molecules at high dilution in argon at 15 K yields species showing intense bands in the i.r. at 800 and 450—650 cm-1. Those at 800 cm"1 showed the appropriate isotopic shifts for assignment of v3 for the ozonide ion, Oj. The use of scrambled isotopic ozones indicates that the metal cation is symmetrically bound to the ozonide ion, which contains three O atoms, with two of these equivalent. In addition, calcium and barium mixtures with ozone contain several metal oxide species tentatively identified as (CaO)2, Ca02,BaO, and (BaO)2, respectively.73... [Pg.83]

The group 2A elements (the alkaline earth metals) have higher first ionization energies than the alkali metals do. The alkaline earth metals have two valence electrons (the outermost electron confignration is ns ). Because these two s electrons do not shield each other well, the effective nuclear charge for an alkaline earth metal atom is larger than that for the preceding alkali metal. Most alkaline earth compounds contain dipositive ions (Mg +, Ca, Sr, Ba +). The Be ion is isoelectronic with Li and with He, Mg is isoelectronic with Na and with Ne, and so on. [Pg.304]

Refers to the cation where M denotes an alkaline earth metal atom. "iThe half-reaction is + 2e -------. M(s). [Pg.820]


See other pages where Alkaline earth metal atoms is mentioned: [Pg.194]    [Pg.195]    [Pg.338]    [Pg.72]    [Pg.86]    [Pg.430]    [Pg.194]    [Pg.195]    [Pg.79]    [Pg.88]    [Pg.1687]    [Pg.3014]    [Pg.3015]    [Pg.3018]    [Pg.3023]    [Pg.3029]    [Pg.3029]    [Pg.72]    [Pg.93]    [Pg.194]    [Pg.194]    [Pg.195]    [Pg.310]    [Pg.59]    [Pg.343]   


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