How Many Unpaired Electrons Are Present in a Ground-state Atom From the Alkaline Earth Metal Family:

Element of group ii

The alkaline earth metals (glucinium, magnesium, calcium, strontium, barium, and radium) are the 2d about reactive metals in the periodic tabular array (Tabular array three.vii), and, like the Group 1 metals, have increasing reactivity in the higher periods.

From: Natural H2o Remediation , 2020

Water chemistry

James G. Speight , in Natural Water Remediation, 2020

v.2 Alkaline earth metals

The alkaline earth metals (beryllium, magnesium, calcium, strontium, barium, and radium) are the 2nd nearly reactive metals in the periodic table ( Tabular array 3.7), and, like the Group 1 metals, take increasing reactivity in the higher periods. Beryllium is the only alkaline earth metal that does not react with water or steam, even when the metal is heated to cherry-red heat (approximately 700–800   °C, 1290–1470   °F). in addition, glucinium forms an outer oxide layer (BeO) protects the metal and lowers the reactivity of the metal.

Magnesium exhibits an insignificant reaction with h2o, merely burns reacts with steam to produce white magnesium oxide and hydrogen gas:

${\text{Mg}}_{\left(\text{s}\right)}+{\mathrm{two}\text{H}}_2{\text{O}}_{\left(\text{l}\right)}\to \text{Mg}{\left(\text{OH}\right)}_{\mathrm{two}\left(\text{s}\right)}+{\text{H}}_{2\left(\text{g}\right)}$

Typically, the reaction between a metal and cold h2o will produce the corresponding metal hydroxide. Still, if a metal reacts with steam, like magnesium, the metal oxide is produced as a result of the metal hydroxide decompositon when heated. Thus:

$\text{M}{\left(\text{OH}\right)}_{\mathrm{two}}\to \text{MO}+\text{H}2\text{O}$

The hydroxide derivatives of calcium, strontium, and barium are just slightly water-soluble but produce sufficient hydroxide ions to brand the environment basic and the general equation is:

${\text{M}}_{\left(\text{s}\right)}+{\mathrm{two}\text{H}}_{\mathrm{two}}{\text{O}}_{\left(\text{l}\right)}\to \text{M}{\left(\text{OH}\right)}_{2\left(\text{aq}\right)}+{\text{H}}_{\mathrm{ii}\left(\text{g}\right)}{}^{\left[9\right]}$

If the h2o is hard, the fact that there are 2 types of hard water: (i) include temporary hard h2o and (two) permanent hard water. Temporary hard water contains the bicarbonate ion (HCO₃ ⁻) which forms a carbonate ion (CO_three ^{−   2}) when heated:

${2\text{HCO}}_3{}^{-}\to {\text{CO}}_{\mathrm{iii}}{}^{-\mathrm{two}}\left(\text{aq}\right)+{\text{CO}}_2\left(\text{g}\right),+{\text{H}}_2\text{O}$

The bicarbonate ions react with alkali metal world cations and precipitate out of solution, causing banality scale and bug in h2o heaters and plumbing.

Common cations in hard water include magnesium (Mg^{+   two}) and calcium (Ca^{+   2}). In order to produce soft water, treatment includes the addition of an element of group ii hydroxide, such as slaked lime [Ca(OH)₂] which dissolves in the water to produce a metallic ion (One thousand^{2   +}) and hydroxide ions (OH⁻). The hydroxide ions combine with the bicarbonate ions in the water to produce water and a carbonate ion.

${\text{HCO}}_{\mathrm{three}}{}^{–}+\text{OH}-\to {\text{CO}}_{\mathrm{three}}{}^{2-}+{\text{H}}_{\mathrm{two}}\text{O}$

The carbonate ion then precipitates out with the metal ion to form the metal carbonate (MCO_iii) which forms a precipitate.

The other type of hard water—permanent hard water—contains bicarbonate ions (HCO₃ ⁻) besides as other anions, such as sulfate ions (And so₄ ^{−   2}). To soften permanent water, sodium carbonate (Na_twoCO_iii) is added which results in the atmospheric precipitation of the magnesium ions (Mg^{+   ii}) and the calcium ions (Ca^{+   ii}) as the corresponding metallic carbonates and introduces sodium (Na⁺) ions into the solution.

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780128038109000036

Novel nanomaterials for environmental remediation of toxic metallic ions and radionuclides

Shujun Yu , ... Xiangxue Wang , in Emerging Nanomaterials for Recovery of Toxic and Radioactive Metal Ions from Environmental Media, 2022

two.7 Strontium

Strontium is an alkali metal earth metal with white luster and active chemical properties. It can easily be oxidized into stable and colorless Sr(2). Natural stable isotopes of strontium include ⁸⁴Sr, ⁸⁶Sr, ⁸⁷Sr, ⁸⁸Sr, and 31 unstable isotopes [64]. Amid them, the most common ⁹⁰Sr has the longest life, with a one-half-life of 28.9   years [65].

In a natural surround, Sr is a trace element in the lithosphere composition of the crustal, but information technology is the nigh abundant trace element (375   ppm) in the upper part of the lithosphere. Rocks are the main source of strontium in groundwater, and it is widely distributed in nature. Sr²⁺ is almost the dominant species in the entire pH range, whereas SrOH⁺ exists merely in a strongly alkaline surround [66]. The h2o chemistry blazon of the strontium-rich water environs is a heavy carbon water surround. Water containing Ca^two+ and HCO₃ ⁻ is the nearly widely distributed on earth, and the content of Sr is generally low [67–69]. This is because of the influence of Ca(II) and M(I) on the migration of Sr(II) in a water background. Sr can be released from Ca- and K-rich rocks along with Ca and K under the influence of groundwater and surrounding media. In addition, owing to changes in cation adsorption, Sr is desorbed into water from the surface of highly dispersed particles such as clay materials. The distribution of Sr in water depends on the extent of Sr(II) replaced past Ca(II) in Ca-containing minerals, and the extent of Sr(2) captured by K(I) in potassium feldspar. When Ca(Ii) in the local groundwater reaches the saturation concentration and precipitates, Sr(2) will replace part of the Ca(II) and produce coprecipitates. Hence, the Sr content of carbonate-rich aqueous solution is generally low. In addition, the pH value of aqueous solutions affect the migration ability of Sr(II). Studies accept shown that when the pH is between 7 and viii.five, the concentration of Sr in water is ordinarily higher. In improver, the distribution of strontium-rich rocks, the degree of weathering and fragmentation of stone minerals, water erosion, and temperature touch the migration and transformation of Sr(Two).

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780323854849000029

Metal Hydrides

Holger Kohlmann , in Encyclopedia of Physical Science and Technology (Tertiary Edition), 2003

III.A.two Ternary Principal Grouping Metal Hydrides

Ternary hydrides containing alkaline and alkaline metal earth metals just adopt typical ionic structure types and are very air sensitive. In the post-obit give-and-take Eu and Yb are included equally they are divalent in hydrides but (except binary YbH _ii.iv) and greatly resemble Sr and Ca in their hydrides because of their almost identical ionic radii. EuH₂ and YbH_ii crystallize as the dihydrides of Ca, Sr, and Ba in the PbCl₂ blazon structure. In contrast to the main group hydrides, those with European union are colored (ruddy, brown, or violet) and are ferromagnetic semiconductors. Simple ionic structure types are adopted by many ternary hydrides of the type A _a M _thou H _{a  +   2m} (A   =   Li–Cs, M   =   Mg–Ba, European union, Yb), east.g., the perovskite-type structures. Examples of the latter are RbMgH₃ (hexagonal perovskite (BaTiO_iii) blazon), NaMgH₃ (orthorhombic perovskite (GdFeO₃) type), CsCaH₃, SrLiH₃, BaLiH₃, and EuLiH_three (cubic perovskite (SrTiO_three) blazon). In the last structure (Fig. 2, left) Eu is surrounded by 12   H cuboctahedrally and Li past six   H octahedrally. Despite the unlike stoichiometry in that location is a close relationship to the crystal structure of EuMg₂H_six (Fig. two, correct), a further ternary metal hydride with ionic character. Every other Eu layer is missing in the latter with respect to the quondam as required past the electroneutrality on replacing Li⁺ by Mg²⁺. This surprising structural resemblance may be explained past the diagonal relationship between Li and Mg. Some examples of ternary hydrides with grouping 3a and 4a metals are NaAlH_four (CaWO_four type), NaGaH_iv (CaSO₄ blazon), Na₃AlH_half-dozen (cryolite (Na₃AlF₆) type), and Ca₃SnH₂ (anti-CsCu₂Cl₃ type). The alkaline aluminum and gallium hydrides testify complex anions [AlH₄]⁻, [GaH₄]⁻, and [AlH₆]³⁻ in which hydrogen is covalently bonded to the metallic. These compounds are soluble in ethoxyethane. Alanates with transition metals have also been reported, such as Ti(AlH₄)₄ and Fe(AlH₄)₂, but not structurally characterized. The AlH_iv ⁻ unit of measurement also serves equally a ligand in organometallic complexes. With BeH₂, MgH_ii, and CaH_two, ternary hydrides A(AlH₄)₂ (A   =   Be, Mg, Ca) are formed with a more covalent grapheme. AlH₃ reacts with diborane to give Al(BH₄)_iii and with gallane to give Ga(AlH₄)₃. LiAlH_four is widely used in preparative chemical science equally a versatile reducing agent.

Figure two. View of the crystal structures of the ternary ionic hydrides EuLiH_iii (ii unit cells shown) and EuMg₂H₆. Large spheres represent Eu, center-sized spheres Li and Mg, respectively, and small spheres H. The structure of EuMg₂H₆ (correct) is related to that of EuLiH₃ (left, cubic perovskite type structure) by doubling the c-centrality and omitting every other Eu layer. [Reprinted from Physica B 276–278, H. Kohlmann, Crystal construction solution of hydrides containing ^natEu from neutron powder diffraction data., 288–289, 2000, with permission from Elsevier Science.]

Some ternary primary-group metallic hydrides are very metallic rich and were get-go reported as being new intermetallic compounds with unusual properties, as hydrogen has been overlooked in the Ten-ray construction determination. Mutual sources of hydrogen are the commercially available divalent metals Ca, Sr, Ba, Eu, Sm, Yb used for synthesis, which may contain as much every bit 10–20 at % H. Unrecognized hydrogen content has led to confusion in view of valence electron rules in compounds considered as Zintl phases, e.m., the compounds of the formerly assigned "β-Yb₅Sb₃" type construction. It was shown that the true composition is A₅M₃H (A   =   Ca, Sr, Ba, Sm, Eu, Yb; M   =   Sb, Bi), and the crystal structure and backdrop are in agreement with the ionic formula (A²⁺)₅(One thousand³⁻)_iiiH⁻. Further examples for metal rich principal group hydrides are A_iiiMH₂ (A   =   Ca, Yb; M   =   Sn, Pb) with the ionic formula (A²⁺)_threeM⁴⁻(H⁻)₂. Ba₅Ga₆H₂ contains both a hydride (H⁻) and a cluster anion Ga_{half dozen} ⁸⁻ which satisfies the Wade–Mingos rules. A similar state of affairs seemingly occurs in Na_fifteenYard_{half dozen}Tl₁₈H, and for both compounds the bonding situation is in full agreement with valence electron rules later the hydrogen content is correctly assigned. All these compounds are stoichiometric and have semiconducting or insulating properties. Ternary hydrides with a nonmetal, such as hydride halides AHX (A   =   Ca, Sr, Ba, Eu, Yb; X   =   Cl, Br, I) or Th₆Br₁₅H₇, oxide hydrides (Ba₂₁Ge_iiO_fiveH₂₄), and hydride nitrides (Ba₂HN, Sr₂HN, Li₄NH), volition not be discussed.

Read total affiliate

URL:

https://www.sciencedirect.com/science/commodity/pii/B0122274105004269

Volume 4

Vera Höllriegl , in Encyclopedia of Environmental Wellness (Second Edition), 2019

Introduction

Strontium (Sr) is an element of group ii belonging to grouping II of the periodic classification (diminutive number 38, molecular weight 87.62) and is located between calcium and barium. In its chemical characteristics it resembles calcium and barium and has properties intermediate between these two elements.

The element strontium is named after Strontian, a small town in Scotland, where in 1790 Crawford and Cruickshank get-go recognized strontium every bit a new mineral (strontianite) that differed from other barium minerals. The metallic itself was offset isolated by Sir Humphry Davy in London, England, in 1808.

Strontium tin exist in ii oxidation states: 0 and +   ii; however, under normal environmental weather condition, simply the +   2 oxidation state is stable. Owing to its high reactivity (e.g., with h2o or oxygen) elemental (or metallic) strontium is not found in nature; it exists merely equally molecular compounds of other elements.

There are four isotopes of strontium which occur naturally and are stable. Of these, ⁸⁸Sr is the prevalent grade comprising 82.58% of natural strontium; the other iii stable isotopes and their relative abundance are ⁸⁴Sr (0.56%), ⁸⁶Sr (ix.86%), and ⁸⁷Sr (7.0%). Only ⁸⁷Sr is radiogenic; it is produced past disuse from the radioactive alkali metal rubidium (⁸⁷Rb), which has a half-life of 4.88   ×   10^x  years. Thus, there are 2 sources of ⁸⁷Sr in whatsoever textile: one formed during primordial nucleosynthesis along with ⁸⁴Sr, ⁸⁶Sr, and ⁸⁸Sr, and the other formed by radioactivity of ⁸⁷Rb. A parameter typically reported in geologic investigations is the ratio ⁸⁷Sr/⁸⁶Sr indicating the sources of strontium in environmental samples.

Twenty-9 unstable isotopes are known to be. Of greatest importance are the radioactive isotopes ⁸⁹Sr and ^ninetySr formed during nuclear reactor operations and nuclear explosions past the nuclear fission of uranium or plutonium (²³⁵U, ²³⁸U, or ²³⁹Pu). By emission of a beta-particle with a maximum free energy of 0.546   MeV, ^xcSr with a half-life of 28.78   years decays to the radioactive yttrium (^xcY) isotope, or progeny product. The isotope ⁹⁰Y is a beta particle emitter (2.28   MeV maximum free energy), and to a pocket-size caste for 0.02% of all disintegrations, also a beta-particle and a gamma-ray emitter (2.19   keV). The stable decay product of ^xcY is the zirconium isotope ⁹⁰Zr.

The isotope ⁸⁹Sr with a half-life of 51   days decays to ⁸⁹Y by emission of a beta-particle of 1.495   MeV.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780124095489111959

Material Properties/Oxide Fuels for Low-cal Water Reactors and Fast Neutron Reactors

M. Kurata , in Comprehensive Nuclear Materials, 2012

2.05.3.ii Actinide–Alkaline-Earth Metals

The phase relation between actinides and alkaline-world metals changes with the increase in the diminutive number of the latter. Regarding the Be-related systems, a NaZn₁₃-blazon intermetallic compound (D2₃-structure) is observed in the Th–Be, U–Be, and Pu–Exist phase diagrams. ^one,iv These intermetallic compounds cook congruently near the Exist last and the decomposition temperatures are estimated to exist 2203, 2273, and 2223   K for ThBe₁₃, UBe_xiii, and PuBe_xiii, respectively. Since these data accept at least ±50   Thou error, the decomposition temperatures are reasonably comparable. Figure 4 indicates the U–Exist phase diagram as a typical example quoted from Okamoto, ⁴ which was mainly constructed from the observations of Buzzard. ^xiv The eutectic indicate appears nigh the U last at 1363   K, and a narrow liquid miscibility gap appears most the Be terminal in the U concentration region between ∼0.vii and ∼2.ii   at.%. Although the latter was questioned past Hansen and Anderko, ¹⁵ there is no other bachelor experimental information for this system. Co-ordinate to Wilhelm et al., ¹⁶ this miscibility gap is thermodynamically unlikely and its presence is possible but if there is a strong clustering in the liquid phase, and thus thermodynamic functions for the U–Be system are estimated by introducing a elementary thermodynamic model. As for the solid phase, a few percent of solid solubility of Be in γ-U was observed. ¹⁴ Besides, a spinodal limerick was given in the key region. ¹⁴ There are two different sources for the Pu–Be system. ^11,17 The significant differences between them are the congruent melting temperature of the PuBe₁₃ and the shape of the liquidus. The latter phase diagram given in Konobeevsky ¹⁷ was then modified based on the several unpublished results obtained at the Los Alamos National Laboratory, as shown by Ellinger et al. ^eighteen The modified Pu–Be phase diagram by Ellinger et al. ¹⁸ was recommended by Okamoto, ¹⁹ who showed phase relations that are more often than not like to those in the U–Be system, although the eutectic temperature lowered to ∼903   1000. In that location is also a small percent solubility of Be in ϵ-Pu (bcc structure). The Thursday–Exist stage diagram was mainly constructed past Okamoto ¹⁹ from the observations by Badaeva and Kuznetsova. ^xx When neglecting the ThBe₁₃ chemical compound, the Th–Exist phase diagram looks similar that of a typical eutectic type, and the eutectic indicate was reported to exist at 1503   K and at 65   at.% Th. However, according to Okamoto, ¹⁹ due to the cursory nature of the work of Badaeva and Kuznetsova, ^twenty the eutectic point is notwithstanding only a rough interpretation. Table 1 summarizes the thermodynamic functions for the Th–Exist, U–Be, and Pu–Be systems, which were estimated past Okamoto ¹⁹ with respect to the liquid phases. The NaZn_thirteen-type intermetallic compound was as well observed in Pa–Be, Np–Exist, Am–Be, and Cm–Be systems. ^21–23 The decomposition temperatures are predicted to be at to the lowest degree higher than 1673   K for the Np–Be system and 1773   K for the Am–Be and Cm–Be systems. Figure v shows the Np–Be phase diagram preliminarily estimated in the present study, assuming the interaction parameter for the liquid phase and the Gibbs energy of formation for NpBe₁₃ are the same as those for the Pu–Be system. It is speculated that the phase relations in the Np–Be system volition take a reasonably similar shape with the Pu–Exist system, with the exception of the Np final. By measuring the thermal arrests for several compositions, specially virtually the Be concluding, the speculated phase diagram will exist modified efficiently.

Figure 4. U–Be stage diagram taken from Okamoto. ⁴

Tabular array i. Thermodynamic functions for actinide–Exist systems

Thou O(Be,liq)   =   0

G O(Th,liq)   =   0

One thousand O(U,liq)   =   0

One thousand O(Pu,liq)   =   0

Chiliad O(Be,bcc)   =   −12   600   +   eight.067T

G O(Be,HCP)   =   −14   700   +   nine.428T

G O(Th,bcc)   =   −13   807   +   6.808T

G O(Thursday,fcc)   =   −17   406   +   9.012T

G O(U,bcc)   =   −9142   +   vi.497T

K O(Be13Th)   =   −14   630   +   four.902T

Thou O(BethirteenU)   =   −17   100   +   half dozen.470T

Yard O(Be13Pu)   =   −24   980   +   9.400T

G ex(Th–Be,liq)   = ten Th(one   − x Th) (13   520   −   830x Th)

G ex(U–Be,liq)   = x U(ane   − x U) (36   100   −   509010 U  −   580x U 2)

Grand ex(Pu–Exist,liq)   = x Pu(1   − x Pu) (10   160)

Note: values are in J   mol⁻ⁱ. T is in M. 10 is mole fraction.

Source: Okamoto, H. In Stage Diagrams of Binary Actinide Alloys; Kassner, M. E., Peterson, D. Due east., Eds.; Monograph Series on Alloy Phase Diagrams No. 11; ASM International: Materials Park, OH, 1995; pp 22–24, 146–151, 164–168, 207–208, 218–219, 246–247, 297–300, 411–412, 423.

Figure v. Hypothetically calculated Np–Be phase diagram.

Regarding the Th–Mg organisation, there are some conflicting bug among the available data. ^24–26 The tentatively assessed phase diagram was given in Nayeb-Hashemi and Clark. ²⁷ However, the stage relations related to the gas stage were not given in the phase diagram, although the humid point of Mg is 1380   K, which is lower than the transition temperature betwixt α-Th and β-Thursday. Ii intermetallic compounds, that is, Thursday₆Mg₂₃ and ThMg₂, exist near the Mg final in the depression-temperature region. At the to the lowest degree, these decomposition temperatures are much lower than that for the ThBe₁₃, suggesting that the stability of the Thursday–Mg compounds is far lower than that of the Thursday–Be compounds. Thermodynamic functions for the ThMg₂ were determined by Novotny and Smith ²⁸ betwixt 692 and 812   K by means of vapor pressure measurement. The derived equation for the Gibbs energy of the formation is

${\Delta }_{\text{f}}{G}^0({\text{Mg}}_2\text{Th})=-59.871\pm 12.979+(63.639\pm 18.000)\times {10}^{-\mathrm{three}}T({\text{kJmol}}^{-1})$

Table two summarizes the thermodynamic values at 750   M. As for the enthalpy and entropy of formation, the higher values in the table were recommended by Nayeb-Hashemi and Clark. ²⁷ A similar phase relation about the Mg concluding was reported for the Pu–Mg system, ³⁰ although the stage relation at high temperature was different. In that location is a miscibility gap for the liquid phase in the loftier-temperature region of the Pu–Mg arrangement. On the other paw, there are no intermetallic compounds in the U–Mg system, and the limited solubility even for the liquid phase was shown. ³¹ These facts on the phase relation betwixt actinides and Mg advise that the miscibility between actinides and Mg becomes far poorer than that between actinides and Be. By assuming the systematic variation in the actinide–Mg systems, partial phase diagrams for Pa–Mg, Np–Mg, and Am–Mg systems were proposed by Gulyaev and Dvorshkaya ³² and there is express solubility for the solid and liquid phases.

Table 2. Thermodynamic functions for Mg_iiTh

Compound	Gibbs energy (kJ   mol−one)		Excess Gibbs energy (kJ   mol−ane)	Enthalpy of germination (kJ   mol−1)	Entropy of formation (J   mol−i  K−ane)
Mg2Th	−12.14	−14.72	−two.80	−46.89 to −72.85	−45.67 to −81.67
References	28	29	29	28	28

Source: Nayeb-Hashemi, A. A.; Clark, J. B. In Stage Diagrams of Binary Actinide Alloys; Kassner, Chiliad. Eastward., Peterson, D. E., Eds.; Monograph Series on Blend Phase Diagrams No. 11; ASM International: Materials Park, OH, 1995; pp 68–72.

In the cases of the Ca-, Sr-, Ba-, and probably Ra-related systems, the miscibility between actinides and these heavy alkaline metal-earth metals is expected to be very poor even for the liquid phase, although the available information is very limited. Thorium metal was prepared by calciothermic reduction at around 1223   Grand, and the solubility of Ca in Th was establish to be very low (<0.12   at.%). ³³ No binary compounds between U and Ba were observed in the determination of the U–Ba–C ternary stage diagram. ³⁴ The U–Ca, U–Sr, Pu–Ca, Pu–Sr, Pu–Ba, and Am–Ba systems were predicted to be immiscible, and the mutual solubility was extremely low even in the liquid stage. ^11,35–38 Co-ordinate to semiempirical modeling, ^39,40 the express mutual solubility and the absence of whatsoever intermetallic compounds were also predicted for the Th–Ba organisation, although in that location is no bachelor experimental data. These advise that, for the actinides-Ca, -Sr, -Ba, and possibly, -Ra systems, the allotropic transformation temperatures of both the actinides and alkaline-earth metals will only appear in the phase diagrams. Figure vi shows the Pu–Ca stage diagram as a typical example, which was calculated by taking very large positive values (∼50   kJ   mol⁻ⁱ) for the interaction parameters of each phase. Other systems are considered to have a similar tendency.

Figure 6. Calculated Pu–Ca phase diagram by assuming big positive values (∼l   kJ mol⁻¹) for the interaction parameters of each phase.

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/commodity/pii/B9780080560335000136

Surface and Interface Chemistry of Clay Minerals

B. Baeyens , G. Marques Fernandes , in Developments in Clay Science, 2018

5.1.2.2 Surface complexation of cations on clay minerals

With the exception of the alkaline metal and alkaline-earth metals, most metallic ions such equally transition metals, lanthanides, and actinides class surface complexes at the edge sites of dirt minerals. Surface complexation reactions on generic edge sites tin can exist written as:

(5.5) $\text{≡}{\mathrm{Southward}}^{\mathrm{s}}OH+{\mathrm{Me}}^z+y{\mathrm{H}}_{\mathrm{two}}\mathrm{O}\iff \text{≡}{\mathrm{S}}^{\mathrm{s}}O\mathrm{Grand}\mathrm{due\; east}{\left(OH\right)}_y^{z-\left(y+\mathrm{one}\right)}+\left(y+1\right){\mathrm{H}}^{+}$

where Me is a metallic with valence z, y is an integer, and the corresponding surface stability constant is expressed as ^S M _y . For y  =   0 the surface complex is S^SOMe^{(z  −   1)}.

In a nonelectrostatic model, the corresponding surface complexation constant, ^Southward K _y can exist expressed as:

(v.6) ${}^{\mathrm{s}}{G}_y=\frac{\left[\equiv {\mathrm{S}}^{\mathrm{southward}}\mathrm{OMe}{\left(\mathrm{OH}\right)}_y^{z-\left(y+\mathrm{one}\right)}\right]}{\left[\equiv {\mathrm{Southward}}^{\mathrm{southward}}\mathrm{OH}\right]}\cdot \frac{f_{\equiv {\mathrm{South}}^{\mathrm{south}}\mathrm{OMe}{\left(\mathrm{OH}\right)}_y^{z-\left(y+1\right)}}}{f_{\equiv {\mathrm{Due\; south}}^{\mathrm{southward}}\mathrm{OH}}}\frac{{\left\{\mathrm{H}\right\}}^{\left(y+\mathrm{one}\right)}}{\left\{{\mathrm{Me}}^z\right\}}$

where [ ] are concentrations, f are surface activity coefficients, and { } are aqueous activities. In virtually adsorption models, the surface action coefficient is causeless to be unity (e.thousand. Dzombak and Morel, 1990). The chemic equilibrium is very often solved using a arrangement of simultaneous equations and nonlinear to the lowest degree squares optimisation routines (Westall, 1982). The model results (best fit parameters) are then compared with the experimental data plotted every bit solid/liquid distribution coefficient (R _d, L/kg) as a function of pH or as Me adsorbed (mol/kg) every bit a function of Me equilibrium concentration (Me_eql, M). Table v.2 gives examples of selected adsorption models of heavy metals on clay minerals described in the open literature.

Table 5.2. An overview of adsorption of heavy metals on dirt minerals by surface complexation

Clay	Model		Site types	Heavy metals	References
Smectite	NEM	2 pK a	2 sites	Cd	Zachara and Smith (1994)
Mt	NEM	2 pK a	Strong/weak	Ni, Zn, Eu, Sn, Am, Np, U	Bradbury and Baeyens (2005a)
Mt	EM	2 pK a	Stiff/weak	Ni, Zn	Kraepiel et al. (1999)
Mt	EM	4 pGrand a	AlOH SiOH	U	McKinley et al. (1995)
Mt	EM	2 pK a	1 site K SOM	Pb, Cd	Barbier et al. (2000)
Mt	DLM	3 pK a (two AlOH, SiOH)	AlOH SiOH	Np	Turner et al. (1998)
Mt	EM	4 pK a	B-type surface; SiT–AlOc–SiT border sites (Site Hthree)	U	Tournassat et al. (2018)
Illite	2SPNE SC/CE	ii pK a	Potent/weak	Ni, European union, Am, Sn, Pa, Np, U	Bradbury and Baeyens (2009a,b)
Mt mica alumina	ECCM	three pGrand a (K A1, Thou si1 and G si2)	AlOH and SiOH	U	Kowal-Fouchard et al. (2004)
Mt	CCM	ii pChiliad a	2 sites	Cu	Stadler and Schindler (1993)
Beidellite	TLM		2 sites (AlOH and SiOH)	U	Turner et al. (1996)

EM, electrostatic model; DLM, diffuse layer model (Dzombak and Morel, 1990); ECCM, (extended) constant capacitance model (Nilsson et al., 1996); NEM, nonelectrostatic model; TLM, triple-layer model (Hayes et al., 1991).

Read full affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780081024324000056

Chain Polymerization of Vinyl Monomers

R.P. Quirk , in Polymer Science: A Comprehensive Reference, 2012

3.17.2.ii.i Alkali metals

The direct use of alkali metals and alkaline metal earth metals as initiators for anionic polymerization of 1,3-diene monomers equally first reported in 1910 is primarily of historical involvement because these are uncontrolled, heterogeneous processes. ⁴⁶ An important milestone in the evolution of the scientific discipline and applied science of anionic polymerization was the discovery reported in 1956 by Stavely et al. ⁴⁷ at Firestone Tire and Safety Company that polymerization of neat isoprene with lithium dispersion produced high cis-1,iv-polyisoprene, like in structure and properties to Hevea natural rubber. This discovery led to the development of commercial anionic solution polymerization processes using alkyllithium initiators. It is noteworthy that loftier 1,four-stereospecificity in anionic 1,3-diene polymerization is simply observed for lithium in hydrocarbon solution; loftier vinyl microstructure predominates with other alkali metals and in polar media.

The mechanism of anionic polymerization of styrenes and ane,3-dienes initiated by alkali metals has been described in detail by Szwarc. ⁴⁸ Initiation is a heterogeneous process occurring on the surface of the metallic (Mt) past reversible transfer of an electron to adsorbed monomer (M) as shown in Scheme 3 . The initially formed radical anions (M^•−) rapidly dimerize to grade dianions. Monomer add-on to these dianions forms adsorbed oligomers that desorb and continue chain growth in solution. Unlike homogeneous anionic initiation processes with organometallic compounds, this heterogeneous initiation reaction continues to generate new active chain ends during the course of the subsequent propagation reactions. Consequently, there is piddling control of molecular weight, and relatively broad molecular weight distributions have been reported for the soluble polymer obtained from these bulk polymerizations (Yard _w/Yard _northward  =   3–ten); ⁴⁹ a high degree of branching and a high gel content (45%) take likewise been reported for these processes. ^47,49

Scheme 3. Mechanism of metal-initiated anionic polymerization.

These reactions are useful for the preparation of homogeneous difunctional initiators from α-methylstyrene in polar solvents such equally THF. Because of the depression ceiling temperature of α-methylstyrene (T _c  =   61   °C), ⁵⁰ dimers or tetramers can exist formed depending on the alkali metal system, temperature, and concentration. Thus, the reduction of α-methylstyrene by sodium/potassium alloy in THF produces the dimeric dianionic initiators in THF, while the reduction with a sodium mirror forms the tetrameric dianions as the primary products. ⁵¹ The structures of the dimer and tetramer correspond to initial tail-to-tail add-on to class the most stable dianion as shown in Scheme four . ⁵¹ These dianionic initiators are formed and used in polar solvents such as THF.

Scheme four. Germination of dimeric and tetrameric dianions by reduction of α-methylstyrene.

Read total affiliate

URL:

https://www.sciencedirect.com/science/article/pii/B9780444533494000765

Natural and Engineered Clay Barriers

Ian C. Bourg , Christophe Tournassat , in Developments in Clay Science, 2015

half-dozen.4.5 Cation Diffusion

Experimental data on the diffusion of alkali and alkaline earth metals (Na ⁺, Cs⁺, Srⁱⁱ⁺) in clay materials are compiled in Figures half dozen.7–half-dozen.10. Data on α versus ρ _b,clay are shown in Figure 6.7, with each figure corresponding to a different ion. The dashed lines in Figure 6.seven are calculated based on the assumption that cation adsorption tin be described with a linear adsorption coefficient K _d = q/C _b, which yields:

Figure six.7. Experimental information on α equally a role of ρ _b,clay for (a) Na⁺, (b) Cs⁺, and (c) Sr²⁺ in bentonite equilibrated with a 0.ane mol   L⁻¹ NaCl solution (filled red symbols (gray in impress versions)) and in clay-rocks equilibrated with constructed groundwater (open blueish symbols (calorie-free grayness in print versions)).

Figure 6.viii. Experimental data on d(α)/d(log I) as a office of ρ _b,dirt for (a) Na⁺, (b) Cs⁺, and (c) Sr²⁺ in bentonite (filled red symbols (gray in print versions)) and in clay-rocks (open blue symbol (lite grayness in print versions)).

Figure half-dozen.9. Experimental data on D _a/D ₀ as a function of ρ _b,dirt in bentonite for (a) Na⁺, (b) Cs⁺, and (c) Sr²⁺ (filled greenish symbols (dark gray in print versions): all-time available data; stake blue symbols (gray in print versions): data obtained with no sampling of concentration profiles in the clay; open orange symbols (lite grayness in print versions): data obtained from TD or ID methods without accounting for the influence of filter-plates).

Effigy 6.10. Experimental data on (D _a/D ₀)_anion/(D _a/D ₀)_water as a role of ρ _b,clay for (a) Na⁺, (b) Cs⁺, and (c) Sr^two+ in bentonite (filled red symbols (dark gray in impress versions)) and in clay-rocks (open blue symbols (light gray in print versions)).

(half-dozen.17) $\alpha =\mathrm{\varphi }+{\rho }_{\mathrm{b}}{K}_{\mathrm{d}}$

According to Eqn (vi.17), the α values of cations should increase with ρ _b (and with ρ _b,clay, if f _clay is stock-still) as observed experimentally in Figure vi.vii in the case of bentonite equilibrated with a 0.one mol   L⁻¹ NaCl solution. The dashed lines in Effigy 6.7 were calculated using K _d values called to subclass reported α values in bentonite. Results yield K _d = 3–11 dm³  kg⁻¹ for Na⁺, 50–thousand dmⁱⁱⁱ  kg⁻¹ for Cs⁺, and 70–220 dm³  kg⁻¹ for Sr²⁺. The large range of K _d values associated with Cs⁺ improvidence data may reflect the existence of different adsorption sites on clay mineral surfaces with very different affinities for Cs⁺ (Figure 6.two). This may complicate the interpretation of Cs⁺ diffusion information by causing meaning adsorption competition effects (Jakob et al., 2009) and a strong impact of cesium concentration on Cs⁺ diffusion properties (Gimmi and Kosakowski, 2011). The α values of cations in clay-rocks are roughly i order of magnitude lower than in bentonite, with pregnant besprinkle. This divergence is consistent with the lower specific surface area of the clay fraction in clay-rocks than in bentonite (because of the collapsed interlayer spaces of illite) and, also, with the college ionic strengths used for improvidence measurements in clay-rocks (0.1–0.24 mol   L⁻¹, in the example of dirt-rocks data reported for Cs⁺ in Figure 6.7).

Experimental data on the salinity dependence of the α values of cations (Figure six.8) show significant scatter and no clear dependence on ρ _b,clay. Boilerplate reported values of d(log α)/d(log I) for cations in bentonite at 0.1 mol   L⁻¹ NaCl are −0.8 ± 0.3 for Na⁺, −one.0 ± 0.2 for Cs⁺, and −i.2 ± 0.2 for Srⁱⁱ⁺. The first two values are consequent with that expected based on ion exchange theory for a homovalent exchange reaction (d(logα)/d(log I) = −1) (Glaus et al., 2007). The average reported value for Sr²⁺ is significantly less negative than the value of −two expected for a heterovalent Srⁱⁱ⁺–Na⁺ commutation reaction, perhaps indicating that Sr²⁺ adsorption is modulated by the formation of ion pairs such every bit SrHCO₃ ⁺ or SrSO₄ (Cole et al., 2000; Appelo et al., 2010).

Experimental data on D _a/D ₀ for cations in bentonite in the direction parallel to compaction show a strong dependence on ρ _b,clay (Figure vi.9) every bit also reported in the example of h2o and anions. Data on the ratio (D _a/D ₀)_cation/(D _a/D ₀)_water show that the presence of clay minerals has a greater impact on the D _a values of cations than on those of water (Figure 6.10). The ratio (D _a/D ₀)_cation/(D _a/D ₀)_water is essentially identical in bentonite and clay-rocks and is non significantly influenced by ρ _b,clay within the precision of experimental information. For comparing, models that rely on EDL theories with the supposition that Stern layer species (surface complexes) are immobile predict that (D _a/D ₀)_cation/(D _a/D ₀)_water increases with ρ _b,clay (Shainberg and Kemper, 1966; Kim et al., 1993), whereas models that business relationship for the slower diffusivity of h2o molecules located in direct contact with clay mineral surfaces predict a slight increment in (D _a/D ₀)_cation/(D _a/D ₀)_h2o with ρ _b,clay (Bourg et al., 2007; Bourg and Sposito, 2010).

Every bit ρ _b,clay and I approach zero, experimental information on (D _a/D ₀)_cation/(D _a/D ₀)_water should yield an gauge of the ratio of cation diffusion coefficients on the clay mineral surfaces and in bulk liquid water (Bourg et al., 2007, 2008; Bourg and Sposito, 2010). The boilerplate values of (D _a/D ₀)_cation/(D _a/D ₀)_h2o reported inEffigy 6.10 at ρ _b,clay < 1.2 kg   dm⁻³ and I = 0 mol   L⁻ⁱ equal 0.54 ± 0.xiii for Na⁺, 0.03 ± 0.01 for Cs⁺, and 0.thirteen ± 0.01 for Sr^two+. These values are roughly consequent with information on the electrical conductivity of dilute smectite dispersions, according to which adsorbed Na⁺, Cs⁺, and Ca²⁺ ions are 0.55, 0.15, and 0.15 times as mobile as the same ions in bulk water, respectively (Cremers, 1968). These values too are consequent with MD simulations of Na⁺/Ca²⁺-smectite external basal surfaces (where Na⁺ outer-sphere surface complexes, the main adsorbed Na⁺ species, diffuse 0.48 ± 0.08 times every bit fast every bit in majority liquid water (Bourg and Sposito, 2011a)) and of Na⁺-smectite interlayer nanopores (where Na⁺, Cs⁺, and Sr²⁺ diffuse 0.24 ± 0.14, 0.06 ± 0.03, and 0.13 ± 0.07 times equally fast equally in bulk liquid water, on average, in the two- and three-layer hydrates (Bourg and Sposito, 2010)). These results clearly demonstrate that adsorbed Na⁺ ions retain a significant mobility (van Schaik et al., 1966; Gimmi and Kosakowski, 2011), in contradiction with the assumptions of several modeling studies (Jo et al., 2006; Leroy et al., 2006). The much lower mobility of adsorbed Cs⁺ versus Na⁺ may exist related to meaning differences in adsorption behavior, as Na⁺ and Cs⁺ tend to form outer- and inner-sphere surface complexes, respectively, on clay mineral basal surfaces (Marry et al., 2008a; Bourg and Sposito, 2011b).

Salinity has essentially no impact on the D _a/D ₀ values of cations as shown in Figure half-dozen.xi. (Salinity impacts D _e, yet, because of its effect on α.) This beliefs contrasts with that of anions (Figure half dozen.six(c)). This difference between the salinity dependence of D _a for cations and anions is consequent with Gouy–Chapman theory, according to which salinity has a much stronger impact on the characteristic length scale associated with anion exclusion than on that associated with cation adsorption, a phenomenon known as counterion condensation (Sposito, 2004). Experimental information on the activation free energy of diffusion of cations (Figure half dozen.12) point that the T-dependence of D _a in bentonite is significantly greater than in bulk liquid water at ρ _b,clay > 1.three kg   dm⁻³, as also observed for anions in Effigy vi.vi(d). Medico simulations advise that this increase in Due east _a results from cation diffusion occurring predominantly in interlayer nanopores (2- and three-layer hydrates) at ρ _b,dirt > 1.iii kg   dm⁻ⁱⁱⁱ and predominantly on external basal surfaces of dirt mineral particles at lower degrees of compaction (Holmboe and Bourg, 2014).

Effigy vi.eleven. Experimental data on d(D _a/D ₀)/d(log I) for (a) Na⁺, (b) Cs⁺, and (c) Srⁱⁱ⁺, plotted as a function of ρ _b,clay in bentonite (filled red symbols (gray in print versions)) and clay-rocks (open up bluish symbols (low-cal gray in impress versions)).

Effigy six.12. Experimental data on the activation energy of improvidence Due east _a as a function of ρ _b,clay for Na⁺ (yellow diamonds (light gray in print versions)), Cs⁺ (green triangles (night grey in print versions)), and Sr^two+ (blue squares (gray in impress versions)) in bentonite.

Read full chapter

URL:

https://www.sciencedirect.com/science/article/pii/B9780081000274000061

Volume 5

Jie Li , in Encyclopedia of Geology (2nd Edition), 2021

Lithophile Elements

The majority of the refractory elements, including the alkaline-earth metals, more than than 15 lanthanides, and 15 actinides, are nominally lithophile. These elements are enriched in the BSE. With rare exceptions, the abundances of the refractory lithophile elements in the core are negligible (Table 2 and Fig. eight).

A number of volatile elements are lithophile, including alkali metals Li, Na, and K, the lightest alkaline-earth element Be, and the lightest element of group vii F. They are used to ascertain the volatility trend of the majority Earth. Their abundances in the core are also thought to be negligible.

Despite their expected low abundances in the cadre, several nominally lithophile elements have attracted intense interest considering of their potential role in powering the geodynamo. Elements such as uranium (U), thorium (Th), and potassium (K) are important because they are radioactive elements with long half-lives. Fifty-fifty at a trace level of 240   ppm, ⁴⁰K generates ten¹²  W estrus at the present day, enough to drive the geodynamo without any other sources of energy.

Contempo studies suggest that arable lithophile elements magnesium (Mg), silicon (Si), and oxygen (O) may take entered the core under early super-heated atmospheric condition, then gradually returned to the silicate Earth over billions of years (Mittal et al., 2020). Analogous to the crystallization of the present-solar day inner core, the precipitation of these elements into the lower mantle leaves behind a denser cadre fluid, thus providing a compositional buoyancy source equally additional power to the geodynamo. The precipitation-driven dynamo may exist disquisitional for bridging the gap later on secular cooling falls below the critical level, and before the chemical buoyancy associated with core solidification became available.

Read total chapter

URL:

https://www.sciencedirect.com/scientific discipline/commodity/pii/B9780081029084001594

Nuclear Waste material

Paul Chiliad. Andersen , ... Majid Ghassemi , in Encyclopedia of Energy, 2004

three.13 Strontium

Strontium (Sr, diminutive number 38) is an alkaline earth metal lying beneath calcium in the periodic table. 4 stable isotopes are found in nature, and 16 radioactive isotopes take been produced artificially. Almost of the radioactive isotopes of strontium are brusk-lived and of little interest. The exception is strontium-90 (half-life 29.one years), a beta-emitter that is produced every bit a fission fragment. Much of the radioactivity of SNF results from strontium-ninety. Considering its chemic backdrop resemble those of calcium, strontium-90 tends to concentrate in the basic. It is highly radiotoxic, decaying into yttrium-xc (itself an energetic beta-emitter of moderate radiotoxicity).

Read full chapter

URL:

https://world wide web.sciencedirect.com/science/article/pii/B012176480X004149

markwharb1983.blogspot.com

Source: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/alkaline-earth-metal

Share this post