Ionic compounds valence electrons

Bonding involves just the valence electrons of atoms. Valence electrons are transferred when a metal and a nonmetal react to form an ionic compound. Valence electrons are shared between nonmetals in covalent bonds. 

Chemical bond, atoms, molecules, ionic compounds, valence electrons... 

To date there is no evidence that sodium forms any chloride other than NaCl indeed the electronic theory of valency predicts that Na" and CU, with their noble gas configurations, are likely to be the most stable ionic species. However, since some noble gas atoms can lose electrons to form cations (p. 354) we cannot rely fully on this theory. We therefore need to examine the evidence provided by energetic data. Let us consider the formation of a number of possible ionic compounds and first, the formation of sodium dichloride , NaCl2. The energy diagram for the formation of this hypothetical compound follows the pattern of that for NaCl but an additional endothermic step is added for the second ionisation energy of sodium. The lattice energy is calculated on the assumption that the compound is ionic and that Na is comparable in size with Mg ". The data are summarised below (standard enthalpies in kJ) ... 

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 ... 

These reactions show sulfur in the role of an oxidizing agent. The properties of compounds such as ZnS suggest they contain the sulfide ion, S-2. The formation of this ion again can be expected on the basis of the fact that the neutral sulfur atom has two electrons less than enough to fill the valence orbitals. Acquisition of two electrons completely fills the low energy valence orbitals and solid ionic compounds can be formed. 

Each element in Group 1 of the periodic table has one valence electron. These elements form ionic compounds containing cations. Examples are KCl and Na2 CO3. Each element in Group 2 of the periodic table has two valence electrons and forms ionic compounds containing A cations. Examples are CaC03 and MgCl2. ... 

Zinc forms both ionic and covaient compounds. One important covaient exampie is dimethyizinc, Ztl (CH3)2, a substance that has two Zn—C bonds. Used in synthesis reactions since the mid-1800s, dimethyizinc finds uses today in the preparation of cataiysts and semiconductors. Zinc is in Group 12 of the periodic tabie (configuration [Ar]3 d A ), so it has oniy two vaience eiectrons. Each CH3 group contributes seven eiectrons, giving the moiecuie 16 valence electrons. The bonding framework uses all 16 ... 

To determine oxidation numbers, we assign each valence electron to a specific atom in a compound. This means that the oxidation number of an atom is the charge it would have if the compound were composed of ions. Ionic FeO, for example, would contain Fe cations and 0 anions. Thus, in FeO we assign iron an oxidation number of +2 and oxygen an oxidation number of-2. 

For ionic compounds, crystal field theory is generally regarded a sufficiently good model for qualitative estimates. Covalency is neglected in this approach, only metal d-orbitals are considered which can be populated with zero, one or two electrons. To evaluate (Vzz)vai 4t the Mdssbauer nucleus, one may simply take the expectation value of the expression — e(3cos 0 — for every electron in a valence orbital i/, of the Mdssbauer atom and sum up,... 

The mentioned method for synthesis of oxide-hydroxide compounds (Ni, Cr, Co) is more controllable and enables with production of electrode films definite amounts of components. Therefore it guarantees the reproducibility of their compositions and properties. Using the above method we were able to produce the following oxide compounds zero valence metal and lowest oxidation state oxide-hydroxide compounds in cathode process and oxide-hydroxide compounds (in anode process the oxide compounds consist of highest oxidation state oxide-hydroxide compounds). Both type compounds possesses electronic and ionic conductivity. 

Figure 11.1 Simple model of valency and bonding. The sodium atom (Z = 11) has electronic configuration ls22s22p63s1, drawn simply as (2, 8, 1) (i.e., showing all the n = 2 electrons as a single orbital). Chlorine (Z = 17) is s22s22p63s23p5, drawn as (2, 8, 7). In bonding to form the ionic compound NaCl, the outer (3s) electron of Na is donated to the outer orbital of Cl, giving both a full outer orbital of eight electrons, and leaving the sodium one electron short (i.e., the Na+ ion) and chlorine one extra (Cl-).

In Sections 9-3 and 9-4, we will show you two types of chemical bonds ionic and covalent. It is important to be able to represent compounds in terms of the atoms and valence electrons that make up the chemical species (compounds or polyatomic ions). One of the best ways is to use Lewis symbols and structures. 

The reaction of magnesium, with two valence electrons, and chlorine, with seven valence electrons will produce magnesium chloride. The magnesium must donate one valence electron to each of two chlorine atoms. This leaves a magnesium ion and two chloride ions. All the ions have a complete octet. The ions form the ionic compound magnesium chloride, MgCl2. 

To an increasing weight of the chemical bond factor (ionic and/or covalent bonding) will correspond, as an extreme case, the formation of valence compounds. According to Parthe (1980), a compound CmAn can be called a normal valence compound if the number of valence electrons of cations (ec) and anions (eA) correspond to the relation... 

Conductivity Metals are good conductors of electricity and heat because electrons can move freely throughout the metallic structure. This freedom of movement is not possible in solid ionic compounds, because the valence electrons are held within the individual ionic bonds in the lattice. 

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