Metallic elements ionic bonds

The organometallic compound chemistry of the 2A metals is similar to that of the 1A metals, and ionically bonded compounds predominate. As is the case with lithium in group 1 A, the first 2A element, beryllium, behaves atypically, with a greater covalent character in its metal-carbon bonds. 

The structures adopted by the binary compounds of the Group I or II metals with elements from Groups III—VI, the so-called Zintl-phases, have been reviewed, and the bonding in such species has been discussed in terms of the transition between metallic and ionic bonding.347... 

The type of attractive forces within solids depends on the identity of the unit particle and the chemical bonds it can form. The forces between atoms in a covalent network solid (such as carbon in diamond) are covalent bonds. These bonds result when at least one pair of electrons is shared by two atoms. The forces between atoms within metallic elements (such as iron) are metallic bonds. Electrostatic attractions—also called ionic bonds—are the forces between ions, atoms which have lost one or more electrons to become positively charged ions or which have gained one or more electrons to become negatively charged ions (such as those found in NaCI). Ionic compounds are often known as salts. Covalent, metallic, and ionic bonds are strong chemical bonds. 

Because the ns electrons are close in energy to the (n - 1 )cf electrons, transition elements can use dfferent numbers of their electrons in bonding. Thus, transitton elements have mu/ffp/e oxidstion ststes, and the lower states display more metallic behavior (ionic bonding and basic oxides). The compounds of ions with a partialy filled d sublevel are colored and paramagnetic. 

Section 1 2 An ionic bond is the force of electrostatic attraction between two oppo sitely charged ions Atoms at the upper right of the periodic table espe cially fluorine and oxygen tend to gam electrons to form anions Elements toward the left of the periodic table especially metals such as sodium tend to lose electrons to form cations Ionic bonds m which car bon IS the cation or anion are rare... 

Attempts to classify carbides according to structure or bond type meet the same difficulties as were encountered with hydrides (p. 64) and borides (p. 145) and for the same reasons. The general trends in properties of the three groups of compounds are, however, broadly similar, being most polar (ionic) for the electropositive metals, most covalent (molecular) for the electronegative non-metals and somewhat complex (interstitial) for the elements in the centre of the d block. There are also several elements with poorly characterized, unstable, or non-existent carbides, namely the later transition elements (Groups 11 and 12), the platinum metals, and the post transition-metal elements in Group 13. 

Electrons are not only charged, they also have a characteristic physicists call spin. Pairing two electrons by spin, which has two possible values, up or down, confers additional stability. Bei yllium (Be, atomic number 4) has two spin-paired electrons in its second shell that are easily given up in chemical reactions. Beryllium shares this characteristic with other elements in column two, the alkaline earth metals. These atoms also generally form ionic bonds. Boron... 

Two types of chemical bonds, ionic and covalent, are found in chemical compounds. An ionic bond results from the transfer of valence electrons from the atom of an electropositive element (M) to the atom(s) of an electronegative element (X). It is due to coulombic (electrostatic) attraction between the oppositely charged ions, M (cation) and X (anion). Such ionic bonds are typical of the stable salts formed by combination of the metallic elements (Na, K, Li, Mg, etc.) with the nonmetallic elements (F, Cl, Br, etc.). As an example, the formation of the magnesium chloride molecule from its elemental atoms is shown by the following sequence ... 

E++02, etc where E is an element. The metallic atoms are bonded to the oxygen bridge with ionic bonding. For convenience, differentiation is made between simple and complex inorganic peroxide compds. According to VoPnov (Ref 5) simple peroxide compds also... 

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... 

The nature of a binary hydride is related to the characteristics of the element bonded to hydrogen (Fig. 14.8). Strongly electropositive metallic elements form ionic compounds with hydrogen in which the latter is present as a hydride ion, H. These ionic compounds are called saline hydrides (or saltlike hydrides). They are formed by all members of the s block, with the exception of beryllium, and are made by heating the metal in hydrogen ... 

The magnetic criterion is particularly valuable because it provides a basis for differentiating sharply between essentially ionic and essentially electron-pair bonds Experimental data have as yet been obtained for only a few of the interesting compounds, but these indicate that oxides and fluorides of most metals are ionic. Electron-pair bonds are formed by most of the transition elements with sulfur, selenium, tellurium, phosphorus, arsenic and antimony, as in the sulfide minerals (pyrite, molybdenite, skutterudite, etc.). The halogens other than fluorine form electron-pair bonds with metals of the palladium and platinum groups and sometimes, but not always, with iron-group metals. 

Ans. Onlv hvdrogen. Lithium and beryllium arc metals, which tend to lose electrons (and form ionic bonds) rather than share. The resulting configuration of two electrons in the first shell, with no other shells occupied, is stable, and therefore is also said to satisfy the octet rule. Second-period elements of higher atomic number tend to acquire the electron configuration of neon. If the outermost shell of an atom is the first shell, the maximum number of electrons in the atom is 2. 

Chromium has a similar electron configuration to Cu, because both have an outer electronic orbit of 4s. Since Cr3+, the most stable form, has a similar ionic radius (0.64 A0) to Mg (0.65 A0), it is possible that Cr3+ could readily substitute for Mg in silicates. Chromium has a lower electronegativity (1.6) than Cu2+ (2.0) and Ni (1.8). It is assumed that when substitution in an ionic crystal is possible, the element having a lower electronegativity will be preferred because of its ability to form a more ionic bond (McBride, 1981). Since chromium has an ionic radius similar to trivalent Fe (0.65°A), it can also substitute for Fe3+ in iron oxides. This may explain the observations (Han and Banin, 1997, 1999 Han et al., 2001a, c) that the native Cr in arid soils is mostly and strongly bound in the clay mineral structure and iron oxides compared to other heavy metals studied. On the other hand, humic acids have a high affinity with Cr (III) similar to Cu (Adriano, 1986). The chromium in most soils probably occurs as Cr (III) (Adriano, 1986). The chromium (III) in soils, especially when bound to... 

In general, the bond between a metal and a nonmetal is ionic, whereas the bond between two nonmetals is covalent. In other words, the further apart across the periodic table the two elements are, the more likely they are to form an ionic bond. 

Ionic bonding involves the transfer of electrons from one atom to another. The more electronegative element gains electrons. The less electronegative element loses electrons. This results in the formation of cations and anions. Usually, an ionic bond forms between a metal and a nonmetal. The metal loses electrons to form a cation. The nonmetal gains electrons to become an anion. The attraction of the opposite charges forms an ionic solid. 

---