Metals, monatomic cations

Metals form cations nonmetals form anions C, P, and the metalloids do not form monatomic ions. 

Monatomic cations take the name of the metal from which they are derived. Examples include... 

Figure C.6 shows another pattern in the charges of monatomic cations. For elements in Croups 1 and 2, for instance, the charge of the ion is equal to the group number. Thus, cesium in Group 1 forms Cs+ ions barium in Group 2 forms Ba2+ ions. Figure C.6 also shows that atoms of the d-hlock elements and some of the heavier metals of Groups 13/111 and 14/IV can form cations with different charges. An iron atom, for instance, can lose two electrons to become Fe + or three electrons to become Fe 1. Copper can lose either one electron to form Cu or two electrons to become Cu2+.

The name of a monatomic cation is the same as the name of the element forming it, with the addition of the word ion, as in sodium ion for Na+. When an element can form more than one kind of cation, such as Cu+ and Cu2+ from copper, we use the oxidation number, the charge of the cation, written as a Roman numeral in parentheses following the name of the element. Thus, Cu+ is a copper(I) ion and Cu2+ is a copper(II) ion. Similarly, Fe2+ is an iron(II) ion and Fe3" is an iron(III) ion. As shown in Fig. C.6, most transition metals form more than one kind of ion so unless we are given other information we need to include the oxidation number in the names of their compounds. 

To predict the electron configuration of a monatomic cation, remove outermost electrons in the order np, ns, and (n — l)d fora monatomic anion, add electrons until the next noble-gas configuration has been reached. The transfer of electrons results in the formation of an octet (or duplet) of electrons in the valence shell on each of the atoms metals achieve an octet (or duplet) by electron loss and nonmetals achieve it by electron gain. 

Whereas many metals form monatomic cations, only six nonmetallic elements commonly form anions. 

Naming of the positive ion depends on whether the cation is monatomic (has one atom). If not, the special names given in Sec. 6.3.2 are used. If the cation is monatomic, the name depends on whether the element forms more than one positive ion in its compounds. For example, sodium forms only one positive ion in all its compounds—NaT Iron forms two positive ions—Fc2r and Fe,+. Cations of elements that form only one type of ion in all their compounds need not be further identified in the name. Thus, Na may simply be called the sodium ion. Cations of metals that occur with two or more different charges must be further identified. Fe(NO,)2 and Fe(NO,)3 occur with Fc2+ and Fe3 ions, respectively. If we just call the ion the iron ion, we will not know which one it is. Therefore, for monatomic cations, we use a Roman numeral in parentheses attached to the name to tell the charge on such ion. (Actually, oxidation numbers are used for this purpose, but if you have... 

Monatomic Cations of Representative Metals Representative metals almost always form cations in which the ionic charge equals the group number. This is because the group number is equal to the number of electrons in the highest... 

Thus, disproportionation occurs when a highly electrophilic polyatomic non-metal cation interacts with a nucleophilic base to form, in the first instance, a polyatomic cation of lower charge per non-metal atom (lower fractional oxidation state) and a compound, essentially covalent, formed between the base and the non-metal of the cation, with that non-metal now in a higher oxidation state than in the parent cation. For example It disproportionates to IJ and IF5. With greater availability of base, the polyatomic cation first formed will disproportionate to a lower-charge polyatomic cation and ultimately to the free element from which the parent cation was formed. Similar patterns differing in detail, are observed for metallic polyatomic cations, monatomic transition metal cations in low oxidation states and for all naked electrophilic cations. 

To form monatomic cations, metals lose electrons from the valence shell first. Some main group metals have more than one snbshell of the valence shell occn-pied by electrons, in which case the electrons in the highest subshell of the valence shell are lost first. For example, the lead atom loses its 6p electrons to form Pb. The confignration is thus... 

Nonmetal atoms accept electrons from metal atoms if the metal atoms are available, or else they share electrons they never donate electrons to form monatomic cations. The largest charge on any monatomic cation is 4 -I-, and on any monatomic anion, it is 3 —. 

Naming ions of metals that form ions of more than one charge requires distinguishing between the possibilities. For example, iron forms Fe and Fe ions. We cannot call both of these iron ion because no one would know which of the two we meant. For monatomic cations of variable type, the charge in the form of a Roman numeral is attached to the element s name to indicate which ion we are talking about. For example, Fe is called iron(II) ion and Fe is called iron(lll) ion. This system of nomenclature is called the Stock system. 

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... 

In Chap. 6 we placed Roman numerals at the ends of names of metals to distinguish the charges on monatomic cations. It is really the oxidation number that is in parentheses. This nomenclature system is called the Stock system. For monatomic ions, the oxidation number is equal to the charge. For other cations, again the oxidation number is used in the name. For example, Hg2 + is named mercury(I) ion. Its charge is 24- the oxidation number of each atom is 4-1. Oxidation numbers are also used for other cations, such as dioxovanadium(V) ion, V02". The prefix 0x0- stands for oxygen. Oxidation numbers can be used with nonmetal-nonmetal compounds, as in sulfur(VI) oxide for SO3, but the older system using prefixes (Table 6-2) is still used more often. 

Fig. 10.14 Schematic diagram of the double layer according to the Gouy-Chapman-Stern-Grahame model. The metal electrode has a net negative charge and solvated monatomic cations define the inner boundary of the diffuse layer at the outer Helmholtz plane (oHp).

The names of monatomic cations always start with the name of the metal, sometimes followed by a Roman numeral to indicate the charge of the ion. For example, Cu is copper(l), and Cu is copper(ll). The Roman numeral in each name represents the charge on the ion and allows us to distinguish between more than one possible charge. Notice that there is no space between the end of the name of the metal and the parentheses with the Roman numeral. 

Several of the monatomic cations play important roles in our bodies. For example, we need calcium ions in our diet for making bones and teeth. Iron(ll) ions are found in hemoglobin molecules in red blood cells that carry oxygen from our lungs to the tissues of our bodies. Potassium, sodium, and chloride ions play a crucial role in the transfer of information between nerve cells. Enzymes (chemicals in the body that increase the speed of chemical reactions) ofren contain metallic cations, such as manganese(II) ions, iron(III) ions, copper(II) ions, and zinc ions. For example, Zn " " ions are in the center of the enzyme alcohol dehydrogenase, which is the enzyme in our livers that accelerates the breakdown of the ethanol consumed in alcoholic beverages. 

Many monatomic cations and anions exist. These ions can exist in the gas phase, and many are important in atmospheric chemistry. But we encounter ions most frequently when dealing with the chemistry of substances dissolved in water. For example, sodium atoms lose an electron relatively easily to form the sodium cation, Na+. Because it still has 11 protons, this ion retains the symbol of sodium, yet it does not behave at all fike an atom of sodium. Consider an order of French fries. You may have heard news stories about the high amount of sodium in an order of fries, and concerns have been raised about the possible health effects of too much sodium in our diets. This statement could be confusing, because here the word sodium does not refer to sodium metal. In fact, if we place sodium metal on freshly made French fries, the metal will burst into flame The sodium we hear... 

All common monatomic anions have noble gas configurations. Most monatomic cations of the representative elements (A groups) have noble gas configurations. The d- and /-transition elements form many compounds that are essentially ionic in character. Most d- and/-transition metal cations do not have noble gas configurations. 

Most of the main-group metallic elements have one monatomic cation with a charge equal to the group number in the periodic table (the Roman numeral). Example aluminum, in Group III A, has a monatomic ion Al. ... 

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