Ionic compounds monatomic ions

The oxidation number of an element in a monatomic ion is equal to the charge of that ion. In the ionic compound NaCl, sodium has an oxidation number of +1, chlorine an oxidation number of — 1. The oxidation numbers of aluminum and oxygen in A1203 (Al3+, O2- ions) are +3 and —2, respectively. 

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... 

Ionic compounds are named with the cation (positive ion) first. Nearly all cations in inorganic chemistry are monatomic, meaning they just consist of one atom (like Ca2+, the calcium ion.) This atom will be a metal ion. For common ionic compounds, the alkali metals always have a 1+ charge and the alkali earth metals always have a 2+ charge. 

Binary ionic compounds are compounds composed of two monatomic ions. These usually are a metallic cation and a nonmetallic anion. When naming these compounds, there are a few rules that need to be followed ... 

Ternary ionic compounds are ionic compounds containing one or more polyatomic ions. The possible combinations are a monatomic cation bonded to a polyatomic anion, a polyatomic cation bonded to a monatomic anion, or a polyatomic cation bonded to a polyatomic anion. There are additional rules that must be added to the rules in the previous section ... 

To name an ionic compound, name the cation first and then the anion. Use just the name of the element for monatomic cations of elements that form only one cation. For monatomic cations of elements that can form more than one cation, indicated the charge on the cation by a Roman numeral in parentheses added to the name of the element. Polyatomic cations have special names, ammonium ion being the most important. 

Metals with high oxidation numbers tend to act somewhat like nonmetals. For example, many transition metals form oxoanions, such as permanganate ion, chromate ion, and dichromate ion, in which the metal is covalently bonded to oxygen. The ability to form covalent bonds to oxygen is evidence of these metals more covalent nature. (In their low oxidation states, most metals typically exist in ionic compounds as monatomic cations.) Titanium(lV) chloride is an example of a compound in which the... 

Several solid compounds of a predominantly ionic nature have doubly-charged negative monatomic ions as the anions. Foremost among these are the oxides of the stron y electropositive elements of Groups I and II. Relatively fewer of these elements will form compounds with sulfur or selenium with more than 50 % ionic character ... 

Ionic compounds are made from ions, bound by electrostatic forces such that the total charge of the compound is zero. The stoichiometry of an ionic compound is determined by inspection, to satisfy charge neutrality. As mentioned earlier, gas-phase ionic compounds exist, but most ionic compounds are solids in which each ion is strongly bound to a number of the nearest neighbor ions of the opposite sign. An ionic compound is named by listing the name of the cation followed by that of the anion. Ions can either be monatomic or polyatomic the latter are also referred to as molecular ions. 

Some compounds contain polyatomic ions that behave much like monatomic anions. Compounds that contain these ions are called pseudobinary ionic compounds. The prefix pseudo- means false these compounds are named as though they were binary compounds. The common examples of such polyatomic anions are the hydroxide ion, OH , and the cyanide ion, CN. The ammonium ion, NH4+, is the common cation that behaves like a simple metal cation. 

Ionic compounds are composed of cations and anions. The cation is always named first. Naming of the cation depends on whether the ion is monatomic. If not, special names are given, such as ammonium for and mercury(I) ion or mercurous ion for Hg, . If the cation is monatomic, the name depends on whether the element forms more than one positive ion in its compound. For example, sodium forms only one positive ion in all its compounds, NaT Iron forms two positive ions, Fe " and Fe, Cations of elements that form only one type of ion in all their compounds need not be further identified in the name. Cations of metals that occur with two or more different charges must be further identified. For... 

Metal-polyatomic ion Polyatomic ions can take the place of monatomic anions, so formulas that contain a symbol for a metallic element and the formula for a polyatomic ion represent ionic compounds. For example, NaN03 (in solid rocket propellants) and 7 2(504)3 (a foaming agent in fire foams) represent ionic compounds. 

Calcium phosphate, Ca3(P04)2, is an ionic compound that contains monatomic calcium ions, Ca, and polyatomic phosphate ions, P04 . The oxidation number of each phosphorus atom can be determined in two ways. The following shows how it can be done considering the whole formula. 

A binary Ionic compound is one composed of ions from only two elements, one a metal, the other a nonmetal. NaCl, CaF2, and FeCl3 are all binary ionic compounds. Before starting to develop formulas for ionic compounds, it is necessary to know the monatomic ions (ions formed from a single atom) of the common metals and nonmetals. 

Because many ionic compounds are made up of monatomic anions and cations, it is helpful to know how to write the electron configurations of these ionic species. Just as for neutral atoms, we use the Pauli exclusion principle and Hund s rule in writing the ground-state electron configurations of cations and anions. We will group the ions in two categories for discussion. 

Polyatomic Ions Covalent Bonds Within Ions Many ionic compounds contain polyatomic ions, which consist of two or more atoms bonded covalently and have a net positive or negative charge. For example, the ionic compound calcium carbonate is an array of polyatomic carbonate anions and monatomic calcium cations attracted to each other. The carbonate ion consists of a carbon atom covalently bonded to three oxygen atoms, and two additional electrons give the ion its 2- charge (Figure 2.15). In many reactions, a polyatomic ion stays together as a unit. 

Compounds Formed from Monatomic Ions Let s first consider how to name binary ionic compounds, those composed of ions of two elements. 

The central idea of the ionic bonding model is the transfer of electrons from meted atoms to nonmetal atoms to form ions that come together in a solid ionic compound. For nearly every monatomic ion of a main-group element, the electron configuration has a filled outer level either two or eight electrons, the same number as in the nearest noble gas (octet rule). 

If energy is required to form monatomic ions from metals and nonmetals, why do ionic compounds exist ... 

We define the oxidation states (or oxidation numbers) of the atoms in a covalent compound as the imaginary charges the atoms would have if the shared electrons were divided equally between identical atoms bonded to each other or, for different atoms, were all assigned to the atom in each bond that has the greater attraction for electrons. Of course, for ionic compounds containing monatomic ions, the oxidation states of the ions are equal to the ion charges. 

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