Monatomic cations of representative

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... 

Stock system (6.2, 16.2) The nomenclature system for inorganic compounds in which the oxidation state (or charge for a monatomic cation) is represented as a Roman numeral in the name of the compound, stoichiometry (10.1) The determination of how much a reactant can produce or how much of a product can be produced from a given quantity of another substance in a reaction. 

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. 

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. 

The enthalpies of formation of aqueous ions may be estimated in the manner described, but they are all dependent on the assumption of the reference zero that the enthalpy of formation of the hydrated proton is zero. In order to study the effects of the interactions between water and ions, it is helpful to estimate values for the enthalpies of hydration of individual ions, and to compare the results with ionic radii and ionic charges. The standard molar enthalpy of hydration of an ion is defined as the enthalpy change occurring when one mole of the gaseous ion at 100 kPa (1 bar) pressure is hydrated and forms a standard 1 mol dm-3 aqueous solution, i.e. the enthalpy changes for the reactions Mr + (g) — M + (aq) for cations, X (g) — Xr-(aq) for monatomic anions, and XOj (g) —< XO (aq) for oxoanions. M represents an atom of an electropositive element, e.g. Cs or Ca, and X represents an atom of an electronegative element, e.g. Cl or S. 

In Chapter 6, we learned how to name cations. In the Stock system, the charges on monatomic ions were used to distinguish between different ions of the same element. For example, Cu and Cu are named copper ion and copper(ll) ion, respectively. The Roman numeral actually represents the oxidation number, not the charge on the ion. Of course, for monatomic ions, the charge is equal to the oxidation number, and thus we used the charge to determine which Roman numeral to use. By using oxidation numbers, however, we can extend our compound-naming ability to include compounds other than those of monatomic ions. For example, Hg2 is called the mercury(I) ion because the oxidation number of each mercury atom is +1. 

An atomic ion or monatomic ion is one that consists of just one atom with a positive or negative charge. The loss of one or more electrons from an atom yields a cation, an ion with a net positive charge. For example, a sodium atom (Na) can readily lose an electron to become a sodium cation, which is represented by Na ... 

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