Ionic block metals

The ionic model, the description of bonding in terms of ions, is particularly appropriate for describing binary compounds formed from a metallic element, especially an s-block metal, and a nonmetallic element. An ionic solid is an assembly of cations and anions stacked together in a regular array. In sodium chloride, sodium ions alternate with chloride ions, and large numbers of oppositely charged ions are lined up in all three dimensions (Fig. 2.1). Ionic solids are examples of crystalline... 

Carbon forms ionic carbides with the metals of Groups 1 and 2, covalent carbides with nonmetals, and interstitial carbides with d-block metals. Silicon compounds are more reactive than carbon compounds. They can act as Lewis acids. 

Where the lanthanide ionic radius and the macrocyclic cavity are incompatible, though in hydrous conditions the crown ether is likely to be displaced by water ligands, the crown may still be present in the structure of the crystal as a hydrogen-bonded adduct. This behaviour is seen in [Gd(N03)3(H20)3]-(18-crown-6).445 This type of compound is quite well known in the case of s block metals also, e.g. [Mg(H20)6]Cl2 (12-crown-4)454 and, a more subtle case, [Ca(nitrobenzoate)2(benzo-15-crown-5)]-3H20(benzo-15-crown-5)455 in which an apparent 2 1 complex has only half its crown ligand coordinated to Ca2+. 

Now we can work out the formula of an ionic compound formed between the monatomic ions of two main-group elements, one a metal and the other a nonmetal. Unless a lower oxidation number is specified (as for the p-block metals), the metal atom loses all its valence electrons, and the nonmetal atom gains enough electrons to complete its valence shell. Then we adjust the numbers of cations and anions so that the resulting compound is electrically neutral. A simple example is calcium chloride. The calcium atoms ([Ar]4s2) each lose two electrons, to form... 

The directionality in the bonding between a d-block metal ion and attached groups such as ammonia or chloride can now be understood in terms of the directional quality of the d orbitals. In 1929, Bethe described the crystal field theory (CFT) model to account for the spectroscopic properties of transition metal ions in crystals. Later, in the 1950s, this theory formed the basis of a widely used bonding model for molecular transition metal compounds. The CFT ionic bonding model has since been superseded by ligand field theory (LFT) and the molecular orbital (MO) theory, which make allowance for covalency in the bonding to the metal ion. However, CFT is still widely used as it provides a simple conceptual model which explains many of the properties of transition metal ions. 

Table 2.1 Valence shell electron configurations, first and second ionization energies E, atomic radii and some ionic radii of the d-block metals...

The effective ionic radii of several d-block metal ions are summarized in Table 2.8. Explain the underlying cause of the pattern of variation among these radii. 

The magnetic properties of d- or f-bloek metal ion complexes can usually be predicted from ionic bonding models. Orbital contributions to magnetism can often be neglected for first row d-block metal ions but must be included when considering f-block metal ions. 

Can be ionic saline), molecular, or interstitial -> Saline carbides are most commonly formed from Group 1 and 2 metals, Al, and a few other metals. 5-Block metals form saline carbides when their oxides are heated with C. 

Ionic liquids with anions containing transition metal complexes were among the earliest developed room temperature ionic liquids [60], Transition metal based ionic liquids have been synthesized either by reaction of phosphonium or imidazolium halides with the corresponding metal halides, or by metathesis with alkali salts of the metal-based anions. Among the metal containing ionic liquids, ionic liquid-crystals are excluded in this section as they were reviewed thoroughly in 2005 [61], Synthesis of metal based salts can be divided in to three groups (1) transition metal salts, (2) p-block metal salts and (3)/-block metal salts. 

Other metal based ionic liquids have included p-block metal based ionic liquid systems based on Sn [77], In [78], Bi [76], Pb [79] have been prepared. In 1986,... 

The overall decrease in atomic and ionic radii (Table 24.1) from La to Lu has major consequences for the chemistry of the third row of J-block metals (see Section 22.3). The contraction is similar to that observed in a period of d-block metals and is attributed to the same effect the imperfect shielding of one electron by another in the same sub-shell. However, the shielding of one 4/ electron by another is less than for one d electron by another, and as the nuclear charge increases from La to Lu, there is a fairly regular decrease in the size of the Af" sub-shell. 

The ionic radius varies with the charge and coordination number of the ion a coordination number of 6 refers to octahedral coordination, and of 4 refers to tetrahedral unless otherwise specified. Data for the heavier d-block metals and the lanthanoids and actinoids are listed in Tables 22.1 and 24.1. 

---